Yes. And if he was about to give forced abortions to a group of Jewish women, I'd kill him for that too.
Course, if they were about to be experimented on by the camp doctor in various grusome ways, there was no escape or way to avoid it, and the guard had decided that putting them out of their misery with a single shot to the head, then I'd probably let him get on with it
Or if he was a doctor turning off the life support for a desperatley ill child who was in terrible pain, I'd ask if I could help.
Or if I was caught in a fire, my legs trapped, and a policemen with a gun came by, I'd be pretty enthusiastic about the whole mercy killing thing. Presumably tho if there were fundies about they would soon put a stop to that and let me roast!
Gee, seems like a blanket "thou shall not kill" is a bit fucking limited when it comes to the real world.
Turning to your real question, if he was a doctor aborting a fetus because the mother wanted him to? To be honest, not sure. Perhaps its none of my business. At the end of the day she can always kill it - best she do it safely.
Edit: the thread this came from has some very good discussion about the legitimacy of killing abortionists, especially the letter quoted on page two. Shows that not all christians lack decency and intelligence