Just read an op ed about this.
And I'll admit, I've been guilty of this. Usually, it's a The Dodo post on Facebook about cute kitties and puppies, and here comes a vegan preaching about not eating animals and how meat eaters are horrible people. My favorite retort of mine is, "Help reduce Earth's carbon footprint. Eat a vegan." They love that.
But yeah, for me personally, I can easily see why vegans get hate. The militant vegans are very forceful, judgmental and condescending. I don't care about vegans who do it for their own reasons. The ones I know personally, great people. But as with religion, you shouldn't try to convert people. I've also interacted with vegans personally who make those "tsk" noises when you eat a burger in their presence.
Does it excuse me from trolling vegans? Not really, even though I view militant vegans as trolls themselves. Yet, I need to admit to myself that I immediately jump to conclusions when I meet a vegan. And that's a bad attitude to have. I should know better not to assume how someone is because of the community they associate with. After all, I'm a gamer, and I get looks from people all the time when I tell them that I am one.