I have a vegan friend who didn't tell anyone he was vegan. I only found out because I asked about his vegetarianism because I was cooking for him.
The reason that most vegans feel the need to talk about it is because it is a life choice that cannot be observed at a glance like tattoos or a style of dress. There's this competitive drive in all of us that makes us want to say that we've done something others haven't, and veganism is one of those things.
I'm a vegetarian, I don't own a car (I don't even use public transportation if it can be avoided), and I try to keep processed foods as minimal in my diet as possible. Cooking spinach is no worse for me than raw spinach. Hot coffee isn't worse for me than cold-press.
Maybe everyone who's saying that it's not about who's wrong or right should hold their tongues lest reality smack them upside the head.