"Libya's mad dog isn't barking now," shrieked the New York Post headline in yesterday's "Libya Extra."

"This evil man," President Reagan fulminated as he defended Monday night's air strike against Col. Muammar Qaddafi, who has been implicated in acts of international terrorism.

A man in Los Angeles tacked a picture of the Libyan leader to his living room wall, aimed his .22-caliber rifle and fired. A radio station in Poplar Bluff, Mo., broadcast a hastily recorded tune, "Message to Muammar," and the switchboard was immediately jammed with requests. "The world can be divided," Qaddafi once observed, "into those who understand me and those who do not know my true nature."

That nature -- whether "flaky," "barbarian," "mad dog" or just plain "evil" -- has provoked a barrage of presidential rhetoric that,some say, inevitably resulted in a barrage of bombs.

"I think in many ways this is a natural response because of the way the media has been playing this thing," said a Middle East-born media specialist who asked not to be identified. "In a sense, the public has been prepared to accept it. The escalation in rhetoric -- saying that Qaddafi is a 'mad dog' -- tends to dehumanize him."

"We know from propaganda exercises in the past that once a simple concept is implanted in the popular folklore -- that Jews are greedy, blacks are lazy, and so forth -- it becomes a reality," says Jack Shaheen, a professor of mass communications at Southern Illinois University. "We begin to accept these images, and they become real."

"I think if the U.S. government calls a foreign leader something long enough and loud enough," says Frank Mankiewicz of the public relations and lobbying firm Gray & Co., "he will almost become it, he will almost be required to. Call a man an extremist leader and a little flaky to begin with, he'll say, 'Gee, maybe I will be.' "

Born of Bedouins in a goatskin tent, Qaddafi arrived on the world scene in 1969 when, as a 27-year-old army officer, he deposed the corrupt Libyan King Idris in a bloodless coup. He quickly emerged as a champion of Pan-Arabism and as the spiritual heir to Egypt's Gamal Abdel Nasser, whom Israel had humiliated in the Six Day War.

As he set about building housing projects and encouraging agricultural innovation, Qaddafi developed the image of "a nationalist populist leader who was really quite popular," says Michael Hudson, director of Georgetown's Center for Contemporary Arab Studies. "He was regarded as one of these revolutionary young technocratic military officers with a strong nationalist ideology -- and we thought he was probably anti-Soviet."

That perception faded as Qaddafi was linked to iron-fisted leadership at home and unorthodox behavior abroad, including his frequent schemes to unite all Arabs under one national banner -- his banner. Georgetown University, which accepted a $750,000 Arab studies grant from Libya in 1976, returned the money in 1981.

"Certainly by the early '80s, the bloom was off the rose," says Hudson. "The evolution of his image followed the evolution of instablity in his own personality. His leadership became much harsher and erratic, mystical, and quite frightening in many ways."

Hudson says that today's American policy makers "really seem to believe that Qaddafi is this evil spirit, and that everything possible must be done to contain him or destroy him. The perplexing thing is that this fixation has distracted us from paying attention to really important political issues in the Middle East."

Mankiewicz says of Qaddafi's image as the avatar of evil, "I think it's television, to tell you the truth. You see the results of terrorism -- maimed bodies and the blown-away walls and weeping American survivors -- and then you see Qaddafi, and he's smiling. It's much more powerful than reading about it."

Mankiewicz adds, "He has the great disadvantage of people who almost speak English and have a large ego -- he thinks he speaks better English than he does. If you listen to him closely, it's clear he doesn't understand many subtleties in speech. He will say things he doesn't mean to say. He may mean something worse, but he uses an inappropriate word. If you want to be a demagogue, you better either speak really good English, or not at all."

Faris Bouhafa of the American Arab Anti-Discrimination Committee casts the conundrum in show-biz terms. "Reagan's style of politics," he says, "has much more to do with entertainment than real politics. Qaddafi also has a certain amount of charisma and views himself as a highly visible public figure, and uses the media to portray a certain image. So what we essentially have are two publicity hounds, competing for your attention. And guess what? You guys in the media love it. You're giving them everything they want.

"This whole debacle between Libya and the United States is so far removed from the real problems of the Middle East that it has almost become a sideshow. What concerns me is that in order to promote this sideshow -- to sell tickets, if you will -- anti-Arab hysteria is being drummed up relentlessly in this country."

The Middle East-born media specialist says the demonization of Qaddafi fits into the larger context of how Arabs in general are perceived in the United States. "There has been a very negative montage," he says. "Either an Arab is a bloody terrorist or else he is the fat rich sheik who has been threatening the West's jugular vein whenever the price of oil goes up."

"Qaddafi is a little unique, you've got to admit that," allows Samih Farsoun, a sociologist at American University. "He is a little bit of a quixotic character perhaps. He wears the traditional garb of Libya or his military uniform. Those two are distinctively different from the American tradition. So he has the image of a strange dresser, the founder of a mass movement with his little Green Book, much like Mao with his little Red Book -- and all these negative images come together."

Beirut-raised Halim Barakat, a Georgetown University political sociologist, says Hollywood has contributed its share. "There have been several films such as 'Delta Force' and 'Harem' that perpetuate the old concept of Arab culture, bent on abusing women, on being involved in terrorist acts and so forth . . . Heroes can come and go. Villains can come and go. But the issues will remain."

As for sweetening Qaddafi's image, Mankiewicz says, "He could do what some congressmen have done -- claim to be an alcoholic. He could then be born again and go into AA. That seems to work. Or he could do like Richard Nixon has done -- have small groups of younger newsmen up to his home. He could get rid of his clothes and wear a three-piece suit. He could cut his hair, have himself photographed at his desk. And hire Mike Deaver.

"Actually, I hate to say this -- being in the business I'm in -- but there comes a time when substance overcomes image. I think Qaddafi is too far gone."