@Steve 41oo,
You could be arrested, if you were lucky. Otherwise, you could have your throat cut.
But, many a true word spoken in jest, eh? You can't insult anyone on the basis of race, ethnicity or religion nowadays (except if they're C of E) by law.
But to some, the most important factor which divides us is allegiance to club. Instead of black vs. white, it's red vs blue or whatever.
So for total social harmony, obviously we need a new law: say we call it Diversity Tolerance Act (Football) 2010. Aggressive chants, insulting songs, lewd gestures, major rucks and mounted police charges at fans will be all in the past, hurrah!