Well, what you two are talking about falls into #2, people who look down on others for eating meat, which isn't what a vegan is.
Like, if a group of friends are getting together and everyone is bringing something to eat, and someone brings a vegan dish, I don't think that is offensive.
People become vegan for a number of reasons, whether it's for their health, ethical reasons, environmental reasons, or influence from family or friends, but really probably being a mixture of them.
Plus a lot of people I know are pretty much part-time vegans, and will enjoy a meat dish every now and then, which they'd probably fall into the health / environmental vegan.
There's always going to be those who think they are superior than others because of something they do or practice, like, being vegan somehow makes you better than everyone else, so you like to make it very clear that you're above them because of the choice you made, or where you live, or a religion, age... gender.... really if someone wants to feel superior over someone else they require little effort in finding something to do so.
What I guess I'm saying is, vegan's aren't horrible people, but horrible people can be vegans.
Also, the people who choose not to be vegan and put down people who are vegan really are no different. Just because the sides are flipped doesn't suddenly give you a right to speak badly about a group of people .-.