As a non vegan, I don't really care too much and maybe even silently admire the commitment to a cause.
However, like with religion, don't try to proselytize or treat me with 'holier then you' disdain. I get that it's more than a diet, and more akin to a lifestyle, however if it's the only thing you talk about it comes across as shallow.
I'd feel the same about someone into Krishna or Jehova. I'm interested to a point but don't mistake my interest for a potential conversion.
But if your at my table I'll do my best to serve you a great vegan meal to the best of my ability nor drone on about how I could never do without x.