I can see how the current song can be seen as offensive, particularly by slavisa himself.
Unless I am mistaken, the connotation that "he'll murder ya" because he's from Serbia is due to the genocide which happened there. Unless there's another reason why he's murder you? Because serbians are hard? Again, that image probably only exists because of that same war.
I don't think this song is any different than singing about nazis to a German player or manager.
At best it's naive and not very imaginative, at worst it's bigoted.