I have to say, I know 6 different 'vegans,' (2 colleagues, 2 family members, and 2 friends,) and they are all quite annoying when it comes to their veganism, and judgy about what others eat. And hilariously, 4 of them aren't even VEGANS. 
They are constantly posting stuff on twitter; preachy shit about how meat is murder, and how it's 'cruel' to eat dairy, and posting (graphic) pics from PETA. Then on the sly, they eat a pizza with cheese on it, or drink a latte.
One young relative of mine gets really pissed off with people saying 'oooh, aren't you sooo healthy, eating fruit for lunch?!' and similar comments, as she feels patronised, but she doesn't help herself by putting shit on her twitter every fucking day about being a 'vegan!' (Which she isn't anyway, as not a week goes by, when she doesn't eat something made from dairy/eggs etc.)
And as has been said, some of them always harp on about it too, like they deserve a medal, and they act meat eaters are evil. I was pissed off when my colleague sent me a link to a documentary film on netflix, saying 'watch this, it's great, it's about healthy eating.' I watched it, and it was basically vegan propaganda .
One story on it made me laugh; an obese 55 year old woman who had suffered arthritis, diabetes, depression, asthma, and IBS for about 20 years, ate this super duper vegan diet for TWO WEEKS, and every single one of her ailments was miraculously cured. IN. TWO. WEEKS.
What a crop of horseshit. Having a much healthier diet would of course help all the ailments, but in 2 weeks? Don't make me laugh! This woman didn't ask me about it. Just as well, as I would have told her it was a load of shit.
Fucks me right off, it truly truly does. They are on a par with people who preach about religion. (Not bashing religion by the way, just people who call at my door and try to convert me!)
I know vegans get fed up of being questioned and moaned at and criticised (by some meat eaters,) but it's no wonder, because some of you don't half like to keep reminding people that you're a 'vegan!'
*disclaimer, not saying ALL vegans (and people who pretend to be vegans) are like this, just the ones I know!!!