The Serbs probably felt that it was better to fight the Islamo-Nazis than pray they will not act like their grandparents.
The failing of the West was that it did not try and be tough on all sides - I don’t buy the argument the Serbs were more brutal than the Croats (who ethnic cleansed more Serbs than vice verse) or Muslims.
You can see the Serbs as committing justifiable homicide. But nearly anyone with a historic grievance rationalizes their actions the same way, the IRA, the PLO, and the NAZIS. Once you step away from moral constraints the way that Milosevic and his followers did, you're likely to become an evil monster.