The tragic murder of Dr. George Tiller by an anti-abortion zealot raises a comparison between the anti-abortion movement and the animal rights movement. It's perhaps no surprise that, despite the fact that anti-abortion activists have murdered several doctors and animal rights activists have yet to murder anyone, animal rights activists are considered the greatest domestic terrorist threat in the United States by the FBI. Animal industry is big business, after all, and abortion not so much. But the question remains: are we animal rightists just as batshit zealous as the anti-abortion nutjobs?
I think a case can be made that we are not, even from the standpoint of the animal-using public. The most obvious difference between anti-abortion and animal rights advocacy is that the former is almost entirely based on religion while the latter is not. The idea that animals feel pain, and that we ought to minimize their suffering, is one that virtually everyone agrees with -- the animal rights position merely draws a more strict line at what suffering is justifiable. In contrast, there is no particularly coherent argument as to why the life of a fetus always takes precedence over the right of a woman not to have her body used without her consent; it's just "God says so." Which is particularly funny since the Christian god kills plenty of pregnant women, fetuses, and babies himself and never actually addresses abortion in the bible. In other words, even if one disagrees with the conclusions drawn, there is something fundamentally rational about the animal rights position that the anti-abortion position lacks in all but its weakest variants.
There is also the fact that the animal rights position, in defense of animals, does not call for violating the rights of humans. The anti-abortion position, however, does call for violating the bodily-autonomy rights of women. People may have a right to earn a living, and to eat, but they don't have a right to any particular occupation or specific choice of food. There are already many moral, legal, and economic restrictions that force people to avoid certain careers and cuisine, and the acceptance of animal rights merely adds to those restrictions. But there is no anti-abortion position that allows women autonomous control of their bodies.
Finally, the mere fact that both the anti-abortion and animal rights movements have elements that believe in the use of violence to achieve their aims doesn't particularly unify them. All movements have elements that believe in the use of violence, and the existence of such elements doesn't validate or invalidate the larger movement. Violence is not a particularly unique characteristic of anti-abortion or animal rights advocacy.
So why are anti-abortion and animal rights activists often described as being similar in terms of both zealotry and dangerousness? I think the comparison is intentional. In my experience, most animal rightists are pro-choice and not particularly religious. Furthermore, most animal rightists are, if not pacifists, prone to nonviolence as a part of their political philosophy. Animal rights violence is exceedingly rare and generally not harmful to people, though property damage is more common. So for supporters of animal industries, the best way to discredit animal rightists is to portray them as equivalent to a movement they share virtually nothing with. This not only paints a certain image in the minds of observers, but it is sure to put animal rightists on the defensive and leave them angry -- which the supporters of animal exploitation can then point to as evidence of their zealotry and instability.