I understand where you are coming from, but instead of judging veganism based on one vegan who harassed you, why not read about the fundamental concepts? Peter Singer or Tom Regan are a good start.
One way to understand why certain vegans act like this, is to learn about Secondary Traumatic Stress Disorder. This is more common than it looks and watching documentaries like Earthlings can definitely trigger it on people who are not well equipped to witness this level of violence.
I am not judging Veganism. I am certainly not doing it on the basis of one extreme example of assholery. But the specific example highlights what is wrong with running around and pissing on other people because you don't approve of their food choices. If vegetarians want to ascribe to themselves the role of moral leader, they need to up their game and figure out how to stop being gratuitous assholes to the millions, if not billions, of animals that are the same species as themselves but don't eat like them.
One way to understand why certain vegans act like this, is to learn about Secondary Traumatic Stress Disorder. This is more common than it looks and watching documentaries like Earthlings can definitely trigger it on people who are not well equipped to witness this level of violence.