It definitely goes both ways with the nagging. I'm a pescetarian (eat seafood, but only very occasionally), and especially in Australia, barbeques and dinner parties can be an absolute nightmare. I always do the decent thing, mention the dietary stuff, offer to make a veggie dish, etc, and that's the alright part. It's when some buttplug who you don't know starts wanking on about "Oh, I don't know how you can't eat meat. I love meat. Do you miss bacon? Everyone loves bacon. I knew someone who was vegetarian, and they missed bacon. You don't miss bacon? How can you not like bacon? Why don't you just try this? Honestly, it's nice, you'll love it, you can't taste the meat in it. It's bacon. ****in' bacon."
It's a bit like when straight people think gay people are only gay because they just haven't met the right person. I just haven't eaten the right dish, apparently! Having said that, it would never be bacon. Bacon's overrated. I do miss blackpudding though!
But I also get how ****ing annoying militant vegans/vegetarians can be. Especially when they're new to the game. Especially when they're trying to tell their Granny how to suck eggs. They eventually get over it. It's the same was when smokers give up cigarettes. They talk about how wonderful life is, how they can smell everything, and how much better they feel because reaffirms their commitment to quit.
And like smokers, meat-eaters get sick of being lectured, but deep down, they do know there is a certain point there about smoking or eating [too much] meat. But constant badgering is not the way to do it.