I don't think the "animal rights" movement is about animals at all. It's about people, and making rules for people. Hence the passion, and the willingness to kill, to have their way.
With the enviralists, like the Smiley Face bomber, there seems to be a lack of humanity, and the idea that animals are "equal" to us consequentially fosters a belief that since humans kill animals, there is a moral equivalency in killing humans. These guys are asocial and seem to make perfect Manchurian candidates - in fact, they need no brainwashing at all.
Absolutely correct.