COMMUNIST tyranny was the ugly monster of the cold war world. The enslaving systems of Marx and Stalin were attacked by intellectuals and writers ranging from Alexandr Solzhenitsyn and Anatoly Scharansky to Czeslaw Milosz and Vaclav Havel. Now the dragon is slain. Witness Poland, Hungary, Czecholsovakia, Germany, and the Soviet Union.But in the post-cold-war world, a new monster is loose. It is wreaking havoc in Yugoslavia, in Soviet republics, and, in the past few weeks, has been seen stalking in Germany. This is the monster of ethnic hate and nationalism - a monster kept at bay for 40 years under the rigid hand of socialism. Last week in western Germany, Lebanese babies were severely burned by skinheads and neo-Nazis - part of a weeks-long rampage against foreign laborers that has hit some 40 towns throughout Germany. In the Yugoslav republic of Bosnia, a campaign to separate Serbs, Croats, and Muslims - who had been living in harmony - is under way. The plight of economic refugees in East Europe and conflict between Russians and native peoples in the Baltics and Central Asia have yet to be resolved. Politicians in East Europe are proving they can be anti-communists without being democrats. While years of intellectual labor have taken place on the question of Marxism, little significant thinking has been done on the question of ethnic conflict and nationalism, and how to deal with it. In this regard, the United States, for all its failures and ethnic foibles, offers some help. The idea of an ethnic melting pot and the historical intention in the US to give all persons equal rights are powerful models, however difficult their practice may be. Many American scholars today argue against the melting pot - saying it is apologist, or contributes to a false "triumphalist" view of US history. But against the backdrop of ethnic animosity in Europe, such views may seem parochial, and the US achievements on race become clearer. The US deserves more credit than it gets on the handling of racial issues. Europe can't recreate an American melting pot. But it must think anew about ethnic and regional relations. The alternative is fragmentation, separation, and the rise of hate-mongers who accrue power by creating enemies of other ethnic groups. People must live with each other not as a means of survival - but as a matter of human rights. How to create the intention to subjugate ethnic and racial passions is the question.