I think his point is that being quick to throw out exaggerated extremist views when describing a group can be tedious (if not offensive) to other members of the group.
Honestly, how many mentally-ill extremists who happen to be vegetarian do you think are going to risk jail time and notoriety just to breed ticks (!) and distribute them hoping to trigger this unusual side effect while knowing that they could just as easily spread other diseases?
Their ethics put harm to animals on the same scale as harm to people, and so they regard the rest of us as complacently witnessing something like mass murder. Just because we entirely disagree doesn't make them crazy, though their ideas make it hard to coëxist with us.
Honestly, how many mentally-ill extremists who happen to be vegetarian do you think are going to risk jail time and notoriety just to breed ticks (!) and distribute them hoping to trigger this unusual side effect while knowing that they could just as easily spread other diseases?