"What about the crimes committed by the Partisans?”
That's a good question. Using the exhibit to whitewash communism is unconscionable.
Actually, the main crime of Communism relevant to the story was the failure of the Yugoslav Communists to de-Ustashify Croatia. The garden-variety war crimes of Tito's partisans are insignificant compared to what the Ustashe did -- the third largest extermination camp in Europe was Jasanovac, dedicated not to the mass-murder of Jews, but to the mass murder of Serbs, and the Ustashe were reprimanded by the SS for showing too much enthusiasm and using too barbaric of methods in their campaign of mass murder.
The adoption of the Ustashe-era flag upon the declaration of Croatian independence had the same sort of effect on the Serbs that adopting the swastika flag as the flag of reunified Germany would have had on Jews, and contributed mightily to the now much-vilified desire of Serbs left in Croatia to secede and join Serbia.