I'm a little ambivalent about all this as well.  The drive of little ethnic groups to form independent nations is problematic at best. The difficulties and chain reactions have been thoroughly discussed here.
But it seems to me that Serbia has forfeited any claims to hegemony over ANYONE.  There's plenty of blame to throw around, but Serbia has repeatedly proven its unfitness to be in a dominating position over any ethnic, racial, religious, national or other group.  They broke the social contract and they can have no further claim to the people they tried to wipe out or the land upon which they live.
I wouldn't let Serbia into the EU until stops wearing a chip on its shoulder, trying to pick fights with everyone, and eliminating anyone it can dominate.  The country has a profoundly immature attitude.
Two poor little picked on bullies: Putin and Serbia.  Good luck and good night.