The antagonism has been gradually building up since 1991 (the first riots in Chechnya). Then, because of many ethnic Caucassian mafias having set foot in Moscow and other central Russian cities. In people's minds the word 'caucassian' means 'criminal'. This notion has at least some basis since many crimes are indeed committed by ethnic Caucassians (I'm not trying to say that Russians do not commit crimes, still there is a rather high crime level among the Caucassians who live in Central Russia). Causassians that Russian see here are either uneducated, arrogant bullies or ultra-rich men in Maybachs with bodyguards. There's noone 'in the middle'. Then, of course, there were several terrorists attacks all committed by the Caucassians, so there is plenty of reasons for hatred.

And this is not mere football hooliganism (though the authorities try their bests to make it appear that way) it's nationalistic. People are manipulated to hate the Caucassians instead of hating their government. And tomorrow there is probably going to be another provocation.