I think it is fair to say that the vast majority of vegans are not the noisy, preachy types, and just go about their daily lives never talking about it unless the subject comes up. Indeed quite a few people I know have been vegan for some time, and the only time it will ever come up as a subject is if they've made something new that they liked, and so shared. I've tried a few recipes, generally ones that don't involve meat substitutes and they've been great.
However from purely anecdotal observations, the shoutiest vegans tend to be ones who have made the decision either directly for environmental reasons, or indirectly through partner or peer pressure. It tends to be this particular group of converts that seem to feel the need to preach to all and sundry, indeed one friend of mine went from being a long time veggie to militant vegan, losing most of his friends in the process (including a fair few vegans).
Now I understand that some people are passionate about making a difference, but meat eating is not the sole cause of man made climate change & impact. Recently I was shouted at by a group of vegan activists outside a McDonalds because I had inadvertently walked across some protest message written in chalk on the pavement. I wouldn't have minded, but I hadn't even gone to said fast food outlet (I refuse to call them restaurants), I'd rather chew my own arm off than eat that crap. Worse still when I asked them, albeit slightly sarcastically, if had they travelled far, at least one had driven from the South West just to attend this shouting match.
I just raised an eyebrow and walked slowly away....