Sen. Edward M. Kennedy's speech to the Democratic midterm conference in Philadelphia Sunday contained many finely crafted ironies. But the greatest of them was external and unintended.

He absolutely stopped the Civic Center cold with a reference to his erstwhile bitter enemy, Jimmy Carter, and Carter's stand for human rights. The Democrats did not love Carter, whose name was hardly mentioned at the gathering. But they love human rights in foreign policy and saw no paradox in their failure to condemn the world's worst current violation of human rights, Israel's savage invasion of Lebanon.

Kennedy did not mention the bombing of Beirut; neither had the other oratorical star of the occasion, Walter F. Mondale. All of the "presidentials" showed lots of profile, but none in courage, on the subject of civilian slaughter.

The resolution adopted on Lebanon reflected the need for "unity" rather than the concern expressed just beneath the surface and around the edges of the conference. The one thing emphasized by every speaker was a pharisaical complacency about being Democrats and not Republicans.

"Let there be no doubt about it," thundered Senate Minority Leader Robert C. Byrd (W. Va.) to a crowd preparing to turn itself inside out for Kennedy, "there is a difference between the two parties."

But on the question of not wishing to offend Jewish voters or put Jewish political contributions at risk, the difference was not discernible.

Between parties, the delegates went back to their hotel rooms to freshen up for further revelry. On the evening news, they saw sickening scenes from Beirut.

One ashen-faced Democratic congressman told a festive group at one of Philadelphia's fine restaurants that he had just seen "unbelievable" footage on the shelling of a Beirut home for retarded children and elderly people. A member of the Jewish lobby sharply reminded him that "Palestinians hide themselves amid the most vulnerable people, so what can the Israelis do?"

Many friends of "presidentials" gave it as their private opinion that what was happening should concern Democrats. "Don't we always stand up for the oppressed?" asked a troubled woman from Ohio at a Morris K. Udall party. But rationalization easily beat anguish in the voting.

A Kennedy partisan said, "Liberal Jews are appalled by what is going on. But we are not saying anything, because we think some good will come out of it. It's a classic case, I guess, of the ends justifying the means."

That is basically the position of Ronald Reagan and especially that of Alexander M. Haig Jr. whose resignation as secretary of state was announced Friday, rocking the conference and giving Democrats momentary feelings of irrelevance.

The president had chosen to express his dismay at the slaughter in Lebanon by withholding his smile at the "photo opportunity" that followed his White House meeting eight days ago with Israeli Prime Minister Menachem Begin. Most Democratic senators assuaged their feelings by railing at Begin behind closed doors.

Kennedy's Massachusetts colleague in the Senate, Paul E. Tsongas, was one of a handful of exceptions. "At what point does the U.S. say, 'This is wrong. For God's sake, enough is enough?' " he asked.

Tsongas presided over the conference's foreign policy workshop Saturday morning. The resolution on Lebanon was the work of Mark Siegel, formerly President Carter's liaison with the Jewish community. The unspoken consensus was that it would be unthinkable for the Democrats to say anything that might disrupt harmony--or expediency.

Rep. Mary Rose Oakar (Ohio), a woman of simple forthrightness, protested that silence about the casualties was indefensible. But Rep. Toby Moffett (Conn.), a Lebanese-American, said that with a few changes the resolution was acceptable. He is a candidate for the Senate against incumbent Republican Lowell P. Weicker Jr., who enjoys much Jewish support.

Democratic National Committee Political Director Ann Lewis said thoughtfully that "any number of people wanted to be second or third in for something strong, but nobody wanted to be first."

The cop-out resolution on Lebanon expressed "regret for the loss of life on both sides," thereby putting the prostrate people of Beirut in the same boat with the aggressors. Moffett's sponsorship, which he later said was "a close judgment call that didn't make me feel very good," ensured passage "without dissent." It was seconded by Rep. Michael D. Barnes (Md.), who is very severe about civilian deaths in El Salvador.

Kennedy frequently expressed humanitarian outrage during the Vietnam years, and his reticence now occasioned secret dismay even among members of his own staff. One asked rhetorically, "What is the difference between cluster bombs in Vietnam and cluster bombs in Beirut?"

But Philadelphia was an oratorical contest. Mondale and Kennedy were after the hearts and minds of the delegates. There was no competition for the conscience of the party.