Thanks for your reply, and that's an interesting perspective.
I have no idea about NBA but, being a Spurs fan and with our affiliations to the NFL, I can relate to the inclusiveness of the American Football franchises. And god knows I wish I'd sometimes 'chosen' a different club - but I'm stuck with Spurs for life now. For better or (probably) worse.
I suppose that what I was trying to say before is that whilst I don't necessarily condone the West Ham fans attitude, I can understand why it exists. And also that West Ham fans are not generally representative of the rest of us.
And I've stuck around here because it's nice to talk football with fans of other clubs sometimes. And Juventus supporters seem more normal, and less arrogant, than supporters of other big clubs. You have your vocal minority, however. But don't we all.