Can the killer of an abortion doctor invoke the necessity defense?

Incoming St. John's law prof Marc DeGirolami responds to Richard Stith's suggestion that the necessity defense might be available to the killer of an abortion doctor:

In the first place, I know of no actual court case in which the necessity defense has functioned as a defense to killing a human being (not even in Dudley & Stephens, when they had to eat the cabin boy to survive).  Professor Stith of course could still say that this is because we don't think rightly about the abortion question.  But I think that this misses the basic thrust of the necessity defense, which is that the evil chosen must outweigh (in some jurisdictions "substantially outweigh" or "grossly outweigh") the evil avoided.  Even if one agrees that abortion is a moral wrong, and even if one agrees with the additional, and different, proposition that it is tantamount to killing a human being (not the position at common law or under the MPC, for whatever it's worth), are we really prepared to say that the evil chosen -- the killing of a doctor -- outweighs (in consequentialist/benefit to society/other moral terms) the evil avoided -- the killing of a fetus (by the doctor).  "Outweighs" could carry both utilitarian/consequentialist overtones (it often does in necessity defense cases) or other kinds of moral overtones.

Prof. Stith might respond that because the abortion doctor has the capacity to perform multiple, maybe hundreds of, abortions, that the necessity defense kicks in on purely consequentialist grounds ('Isn't it better to kill one that 100 may live?')  The difficulties with this position are two, I think.  First, in many jurisdictions, one can't take advantage of the necessity defense unless one thought, reasonably, that the evil chosen would have been effective to abate the danger of the evil avoided.  Here, I don't see how someone who murdered a doctor would think that this would reasonably abate the danger of a fetus, or many fetuses, being killed.  Wouldn't that person realize that women will simply go to other doctors?  Second, it seems to me that there are basic limits on the kinds of consequentialist considerations that can inform the term "outweigh" in the necessity defense context.  And murder, in my view, is certainly one of them.