^Yeah, my sisters couldn't be further from that. My little sister will patiently explain her reasoning if anyone asks, but even though being vegan is a very important part of her life and identity, she never makes it the topic of conversation, never pushes it upon others, and I've never felt judged by her or any of her (massive group) of vegan friends. (She spends a lot of time socializing on vegan message boards and even met her boyfriend through one.)
I don't really see veganism as being extreme, in fact, it's pretty reasonable and more consistent than vegetarianism, I think. You have one simple premise: don't exploit animals. Don't use any product made by or from animals. Easy peasy. The only time I ever got into any kind of debate with my sister over her veganism was when I argued that it is a privileged choice, that some people cannot live without using animals in some way or another. I eventually convinced her of the truth of this, and peace was restored.
I know there are vegans of the fanatical and arrogant type you've encountered, but through my sister I've met a huge number, and none of them have ever been like that to me.