It was June 1967. The Middle East erupted in the Six Day War. In Washington, Hisham Sharabi turned on the morning news. "That was the beginning," he says, "of the week that was. Total defeat."

For this native Palestinian, the quick and complete rout of the Arabs "was an emotional, traumatic turning point. In the following three, four, five weeks my thinking became more and more radicalized." There was no choice, he decided - the Palestinians would have to take matters into their own hands.

From that point, Sharabi's then-quite life changed dramatically until today he is perhaps the most prominent Palestinian American political activist and one of the most prominent voices among the more than 2 million Arab Americans.

The American Jewish Committee, in fact, calls the emerging Arab American lobby "a new challenge to pro-Israel sentiment in the U.S."

Sharabi's pronouncements about the Middle East crisis are now always popular - or diplomatic. It is his opinion, for example, that Egyptian President Anwar Sadat "must be losing his grip psychologically. Like the other fellow, both are going mad. He and [Israeli Prime Minister Menachem] Begin, two mad people." And he believes that "there is no other recourse [for Palestinians] than armed resistance."

Yet this Georgetown professor - who calls himself a "realist radical" - is listened to and respected by the White House, State Department and the Congress. Sadat himself has urged a role for Sharabi in Middle East negotiations, so has Sharabi's personal friend, PLO head Yasser Arafat.

Sharabi speaks as one who lost two members of his family at the time of the 1948 war; he bears a built-in anger. "I don't condemn the use of violence, as such, when it is carried out in a just cause, such as that of the Palestinians," he says.

Born in Jaffa and raised in the comfortable surroundings of a bourgeois family, later educated at the University of Chicago and easily Americanized, Sharabi, 51, holds the Chair of Arab Studies at Georgetown University. He is also the president of the increasingly active National Association of Arab-Americans - the only Arab American group registered to lobby Congress. And as its spokesman, according to one colleague, Sharabi "is able to function as a tactician in this society. There aren't many Palestinians able to do this." Arab Image, Arab Voice

What Sharabi and his organization want to do is change the mood of America from what they feel is a pro-Israel point of view.

His "main task," he says, is to build "a bridge, culturally as well as politically, between the United States and this area of the world in which the United States has such a vital interest."

He also wants to alter the Arab image in this country. "We have an ethnic stereotyping that we cannot afford to tolerate and maintain our self-respect. . . . We're the only ethnic group that some people still find fair play for their heavy-handed jokes."

That attitude, Sharabi says, began to change about five years ago, after a surprising showing by Arab armies in the 1973 war and later with the oil embargo. Several groups around the United States began to rally support for the Arab cause, including churches and various Arab-American federations.

According to an American Jewish Committee study, "the two most prominent Arab American organizations" are the Sharabi-led NAAA (founded in 1972) and the Detroit-based Association of Arab American University Graduates, which Sharabi also helped form shortly after the Six-Day War. "The two groups," says the AJC study, "together with a good many smaller ones, seek to bridge old religious and national divisions and create a sense of Arab American solidarity."

This has never been easy. One NAAA founder, Virginia lawyer Richard Shadyac, for example, dropped out of the organization, saying it "does not represent the Middle Arab American." The majority of Arab Americans are of Lebanese descent, and Christian.

Sharabi says that under the leadership of Joseph Baroody, which ended in May, the NAAA "was finally able to get to its business" after merely trying to survive for several years. It opened a Connecticut Avenue office, hired a lobbyist and set about to try to offset the powerful American Israel Public Affairs Committee (AIPAC).

Still, NAAA has only about 2,000 members, and its reported $250,000 budget last year is small compared to AIPAC's reported $750,000.

"It's hard to be as effective as AIPAC, they've been up here so long and have so many contacts," says a staffer on th Senate Foreign Relations Committee, which heard both sides testify on the Mideast arms sale. "But I think you can say they represent a new force on the Hill."

This month, hoping to bring back proposals on the Lebanon crisis to President Carter, Sharabi plans to lead an NAAA delegation to see Lebanese President Elias Sarkis (if Americans are permitted to travel there because of the fighting), then to Syria to see President Hafez Assad and to Jordan to visit King Hussein.

Of all Sharabi's Middle East contacts - Sadat last November suggested that he represent the Palestinians at Geneva - what might prove to be the most significant may be the man most powers are trying to forget, Yasser Arafat, chairman of the Palestine Liberation Organization. They meet every few months in Beirut and are fast friends.

"on a personal level," says Sharabi, "there is a great genuine affection between us. He hugs me. He hugs everybody. But there is a certain special way that binds us."

Then, a faint smile disappears instantly. Turning grave, the words now coming very firmly, very quickly, Sharabi adds what he's been saying all along to those who will listen: "There will be no solution if he (Arafat) and the organization he represents do not approve of it. The United States and this administration and the Israelis are trying to leave the PLO out of the settlement. They'll not get it. Take it from me." Disinherited, Reborn

"All Palestinians became radicalized after the Six-Day War," Sharabi says."We all passed through the process, in different ways under different conditions." Almost wistfully, he adds, "It's too late in life for me, really, to be a practitioner. I'm an intellectual radical. I deal with theory, with ideas. It's too late for me to even pretend that I live a radical's life. Had this happened to me at age 30 instead of 40, this process of change, it would have probably transformed my pattern of life. I would have moved back there and joined up."

Physically, he looks perfectly fit, despite his age, to be fighting literally for his cause. His close-cropped hair is graying, but the small, wiry man looks especially taut, tough. He swims and does the Canadian Air Force exercises daily.

In the '30s, when he was a young boy, Sharabi, a Moslem, remembers almost all good times. "Typical bouregois family," he says. "Comfortable, blind to the misery that surrounded us." His father was a judge. His home in Jaffa was just a few blocks from the sea, and he often played on the beach - there and at his grandfather's house in Acre. He attended a British kindergarten, a boarding school in Ramallah, another boarding school in Beirut. In 1947, he graduated from the American University in Beirut and took off to the United States to study more. The future seemed bright.

Then shock, anguish. While he was at the University of Chicago, where he took a master's and doctorate, the Palestinians fled. "It came as an obsolute surprise. When I left I had pity for the Jews and I hoped the Palestinians would be merciful with them. I was sure they had no chance facing us. Suddenly, we'd lost everything, lost our country."

His younger brother, who had been in frail health all his life, and his grandfather both died shortly after fleeing to Beirut - "as a result of this shock," says Sharabi. He got to Beirut two days after his brother died.

"The blow was so total, so overwhelming, that for a long while we couldn't see our way back to a solution. An entire generation was rendered impotent. It wasn't until the younger generation had grown up that the resistance movement began. Then we all rallied - young, middle-aged, old, educated, illiterate, peasant, bourgeois. We all galvanized. In a world, the Palestinians were reborn." Terrorism or Heroism?

"What they call terrorism here," says Sharabi, speaking as a Palestinian, "is called heroism among those who have been denied their most basic rights.

"The use of violence is inevitable. When the oppressed are the subject of violence, they have no choice but to use violence. Now there are forms that are politically harmful. These forms I condemn. They might be different things at different times."

One such time was the March PLO raid outside Tel Aviv. "It was politically unfortunate, humanly unfortunate," says Sharabi. "But I fully understand what impelled them to do it."

But that raid, Sharabi says, showed that Palestinians are willing "to hurl their bodies against the monster."

"If they had airplanes or tanks, they would have used them. They're using the same tactics the Jewish resistance used prior to 48 against the British in Palestine. The same tactics Mr. Begin himself describes in his book, 'The Revolt: Story of the Irgun,' the terrorist group, headed by Begin."

For Sharabi, "new consciousness" meant greater activism, as an academic and politician. He founded the Journal of Palestine Studies, a quarterly published in Beriut. (NAAA's new executive director, Jean Abinador, says the journal offered the "historical perspective" he needed "as I moved out of the closet of being an Arab American.")

Sharabi also flourished as a teacher and his classes grew. He had to move to a larger classroom. And still there was an overflow into the corridor.

Sharabi's rising visibility at Georgetown, however, has not been welcomed by all university officials and faculty. The Chair of Arab Studies that he holds was financed last year by a $750,000 grant by Libya's controversial Maummar Qaddafi. And last week, the university announced it was returning a $30,000 grant solicited by Sharabi and others from the Iraqi government; the university said it had received a previous donation for the same purpose.

But Sharabi, again speaking his mind, blasted university president Rev. Timothy S. Healey, who was out of the country when the announcement was made, as a "Jesuit Zionist," adding, "I have a greater stake in the university than he has - 25 years. He's a newcomer. I think he's doing damage to the university and to the Center (for Contemporary Arab Studies) and I'm going to fight that man in every way I can." Begin and Sadat

Sharabi's views on conditions for a settlement in the Middle East are no less impassioned or controversial.

He says of Anwar Sadat: "He should have done one very clear thing. Say I've tried. I've failed. I go back to the Arab fold. Heal the wounds. Especially with Syria. Especially with the PLO, Egypt and Syria are the main allies.

"Instead, Sadat has brought Egypt dangerously close to a bilateral settlement. They've cornering him. They're too clever for him. Peres [opposition leader to Begin, Shimon Peres] can get it out of him. It's better to have Begin there. He's too stupid, too rigid." A bilateral agreement, he adds, "would split the Arab world. Make settlement of the Palestine problem impossible.It would make Israel inflexible indefinitely."

Once Sharabi favored "liberating" all the Palestinians' lost terriroty. A "settlement" represents an adjustment in his thinking as a "radical realist."

"A settlement," he says, must be "based on full rights of Palestinians, particularly self-determination, and complete withdrawal of Israel from occupied areas and total sovereignty for Palestinians. Anything short of that is inadequate. It must include the Gaza Strip and West Bank and East Jerusalem. East Jerusalem is as important as the other two. Without Jerusalem, there is no solution."