HARD ON THE HEELS of Andrew Young's public embrace of the Palestinian issue, delegations of American blacks are racing each other to the Mideast to try out their newly discovered diplomatic wings. Once disencumbered of office, Mr. Young will probably head there himself. People who have been in the area before suspect -- and some hope -- that these blacks will discover how intricately bound the real issues are, and that, as a result, they will be appropriately sobered. But that may not be the only result. The newcomers bring something special to the region: an emotional identification with the Palestinians, whom they perceive as the injured party, or the more injured party, and at the same time a high moral profile and a sense of mission. These last translate into a desire to halt the violence and resolve the Middle East dispute on terms acceptable to Israelis and Palestinians alike.

Is it possible to identify openly with one side and still remain in a position to mediate? Certainly, the particular way blacks came to the Mideast issue last month suggested that the answer was no. The first signs were that the black leaders meant to become a lobby for the Palestinians in the same respect that many American Jews are a lobby for Israel. In this expectation, the Israeli government snubbed a Southern Christian Leadership Conference delegation, and the PLO'S Yasser Arafat greeted the group and gratefully joined it in singing "We Shall Overcome." If this has been the tone of the SCLC's whole mission, one could only have concluded that the black delegation was determined to act as a traditional ethnic lobby. That, of course, is a formula for further polarization in the Mideast and at home as well.

But the SCLC delegation did not follow that script. There is reason to expect, moreover, that subsequent black delegations will not follow it either. The SCLC, besides offering sympathy and solidarity, asked the PLO to accept peaceful coexistence with Israel and to honor a three-month "moratorium on violence." Said District Del. Walter Fauntroy: "We deplore violence wherever it occurs, whether it's a bomb from an aircraft in southern Lebanon or a bomb in a garage in Jerusalem." The PLO found all of this "unfair."

Will these black leaders keep trying to combine the roles of advocate and conciliator? It's a moral and political tightrope, but they should be encouraged to inch further along. The best way to help Palestinians achieve self-determination is to remove the basis for the great fear most Israelis now have that the Palestinians' gain is their inevitable loss, perhaps their destruction. If leaders like Mr. Fauntroy are to seek PLO acceptance of Israel by word and deed -- by removing from its charter the language declaring Israel "null and void" and by stopping the killing -- they would be helping clear the way for the fulfillment of the Palestinians' deepest legitimate desires.