I'm a brony, and I can understand and tolerate the Anti-bronies opinions.
What I can't tolerate, is Anti-bronies who push the thing out on all of the bronies. Even the ones who don't spam stuff everywhere.
For instance, a site is flooded with pony stuff, and an Anti Brony takes it out on ALL bronies.
That's one thing that grinds my gears.
Most Anti bronies have opinions that I can actually agree with, but it's just annoying when they name themselves "Bronyslayerxx23" or something on TF2, then put down a "BAN ALL BRONIES" spray.