As a Melbournite I can attest to the far better behaviour, and general banter between rival fans. I think the reason is there's typically more balanced numbers of fans at each game so you have to either act with an air of good humility and humour, or resort to European like football hooliganism. I'm glad we choose the former.
Unfortunately WA is a two team town, and each week effectively a one team town. Throw into the mix 50k people and excessive pre game whip up (sorry, 'fan engagement') and you're going to generate this kind of behaviour amongst some who still act with this prehistoric tribe mentality.