I took Mrrzy's opening post as heavily tongue-in-cheek rather than in-your-face aggressive. A version of the normal pub talk (in the British Isles anyway) in which men routinely insult each other as a way of being friendly. Which can be risky when you aren't in the right company.
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"I agree with tribal but wonder why in the UK, the aggressive behaviour seems to be more common amongst football than say rugby supporters. "

It's often suggested that this is because in rugby the violence is carried out on the field of play, so spectators don't feel it necessary to indulge in it afterwards. But that can't apply in this case, since the level of violence that seesm routine in ice hockey matches in North America eclipses anything that would be permitted in any rugby match. (Or indeed any ice hockey match elsewhere, I suspect.)

Normally sporting riots tend to be between neighbouring teams playing Derby matches - the odd thing here is that the teams whose clash triggered this riot were so geographically distant. You can't get much further from Vancouver than Boston and still remain in the same continent.