Though the makeup of the fanbase is a big factor, a large part of it is due to the player-base and the environment cultivated in locker rooms at every level of the sport.

If you haven't already; I'd recommend reading this article by Akim Aliu which touches on his experiences in youth, OHL, and the NHL all of which have an overwhelmingly hostile environment for anyone who's not a "good ol' Canadian boy".

Just look at Don Cherry; racist piece of shit former coach, player, and commentator who spent decades spreading hateful rhetoric. And his eventual firing just last year for clearly racist comments provoked widespread opposition in so many hockey circles.

edit: Also, just read up on Mitchell Miller