When vegans can't sell the idea of being vegan to people--with the exception of selling it to people that are already inclined that way--maybe, just maybe, they should look at their sales techniques. Think about street corner preachers that use a megaphone to tell everyone that they're going to hell because they're fags, whores, sodomites, trannies, baby killers, whatever slur you want to use; have they ever, even once, managed to make you consider that maybe being an evangelical Christian was right for you?

Directing slurs at people that aren't vegan isn't going to convince people you're right; it's going to make people hostile and defensive. You're creating an in-group and an out-group; you're reinforcing your own status as a member of the in-group, while being exclusionary of everyone that is not already part of that group, or is not sufficiently committed to that group. It's not even effective as form of negging, because negging has to be subtle.

If you want to sell ideas to people, you need to take advice from people that successfully sell ideas from people. If you don't, well, good luck, 'cuz your gonna need it.