Racial slurs from fans has been a problem in European soccer matches.
They have gone to the "empty stadium" punishment. Offending team has to play a home game with zero fans.
That would put an end to it, really quick.
Racist chants are done by fans nearly every week over there (happened yesterday in the Milan-Napoli game) and they rarely do that unfortunately. It's a great idea and I don't know why they don't do it more. I guess the teams would lose too much money which is why I can't see them ever doing that here.