Those who paid and contribute have for the most part have been respectful but can lay smack down like the best of us.
You do make a great point about the real anti-BYU folk. Even when I was a wee little lad back in the 80s, BYU haters fitted the same mold.
Usually former or very inactive members. Many have an axe to grind. Can't really do it with their neighbors, but a sports team and its fans is more then fair game.
New non-LDS Utah transplants often are swayed into hating BYU. Many have their own schools already and BYU haters love to point out why the new Utah residence should hate BYU as well.
And then there is alcohol. Beer is usually fine, but when Jaegger bombs and the whiskey flow then the real BYU haters really come out. Usually it gets those Utes in trouble with other fan bases as well. Makes you wonder if Utes can hold their liquor, my experience is not well at all.