Sounds like black and white thinking.
Try looking at it from their point of view, Robert. If you believe that life starts at conception, then you believe that a fetus is a Human child. With that being true, then abortion providers are murdering children. If you saw someone murdering a child on the street, would you not feel the need to keep them from continuing? What if society at large said butchering children was within the law? Would you go along with that law, or would your morality cause you to act?
In the eyes of those who act violently towards abortion providers, the abortion providers are on the same level as pedophiles and child killers. An abortion clinic is no different than a death camp.