This sounds more like a problem with people jumping to unfounded conclusions than with vegans, doesn't it? I'll admit I used to be one of those even though I'd never even met a vegan, and now that I have met literally hundreds (used to work in a vegetarian coffee shop) I've yet to meet a single one of these so called militant vegans who won't leave you alone before you've listened to all their arguments about what a bad person you are.
Where I'm at there's a tendency to think of (US) Americans as fat, obnoxious people who will sue their own mother if that will get them some of the money they are so obsessed with, would you say this a problem with Americans or (as I believe) a problem rooted in lazy thinking, stereotyping and general prejudice?