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.