That's the function of the legal system - to report murderers to the police so they can be arrested, tried, and convicted. If the victim was truly in the process of murdering others, was he reported to the police by anyone? And that is the system we live under in the United States - if you have objections to such a system, then you should move to another country where murder is legal (good luck finding one, but that's neither here nor there).
Or are you seriously advocating that people who do things that you don't like can simply be gunned down on the street by anyone who might wish to? I can make a pretty convincing case that tobacco kills 500,000 Americans a year - by your logic, I can shoot any tobacco company executive, worker, truck driver, or store clerk that sells tobacco.
If that is your contention, then I have nothing further to say to you as you are advocating vigilanteism and anarchy.
In his mind, he was protecting the lives of these children. That's not murder in cold blood.
Sorry, but under our current system of laws, abortion is legal and the doctor was practicing a legal profession. If you don't like it, then get representatives elected that believe in the same thing you do and get the law changed. That really is the only option you have under the current system - murdering people in cold blood is NOT a viable option.
Your views on abortion are only relevant as it pertains to what you believe regarding when life begins. It is the whole crux of this discussion.
The original post was not addressed to me, so there is no evidence that the "whole crux" of the discussion was directed toward me personally, or to find out what my views on abortion are. Even if it were, my reply would be simply "none of your business."