A good and nuanced point.....
Well, the constitutionality of banning abortion through the legislative process (provided we could dispense with Roe v. Wade, is interesting).
Technically, one could argue that laws against murder are a matter for the states. Certainly the exact punishment for murder is up to the states but what if a given state's government decided not to punish murder at all?
Surely very few people would object to a federal statue at least mandating that states regard murder as a serious crime provided that there is a situation that makes that law neccessary.
This would certainly be preferrable to armed action by concerned citizens of the offending state intended to restore respect for the right to human life in that state. After all, the right to life is "retained by the people". If the federal government is allowed no role in protecting it, and the democratic proccess has produced and will, for the foreseeable future produced a situation where the state does not respect it then the citizens will be left with little recourse but to recover that right as provided for in the Declaration of Independence. Short of that you would have revenge killings and vigilante action to deal with murderers.
Now if you're fine, as a strict states rights person, with periodic small scale revolts at the state level then this works. Otherwise, the federal government has some, very limited, role in ensuring that states do not trample upon the rights of their residents.
If one is pro-life, one generally regards abortion as equivalent to murder. Exceptions to abortion for the sake of the mother's life and long term health are not murder since they are equivalent to battlefield triage.
If one is only mildly pro-life and does not regard abortion to be nearly as serious as murder then there is ample justification for saying that the separation of powers trumps any need to deal with abortion.
I believe that many Libertarians are only mildly pro-life and do not really regard abortion to be the same as murder. Plenty of others do not care about the issue at all and see abortion as just fine.
Like I said, I do not believe that my position on abortion is in any way, shape or form morally upright. If I really, really, saw abortion as equivalent to chopping up a 1 year old baby in a "clinic" I would be far too busy to have this pleasent conversation.
It is the measure of my selfishness that I am willing to "go to the wall" for my gun rights which I personally enjoy, but not for the life of some nameless fetus I will never know.
I know my position is self-contradictory and maybe you can point out that there is no moral difference between voting for Balart or voting for Gonzales. Given that the Senate rather than the House deals with judicial nominees (all important since the first step is getting rid of Roe v. Wade) Gonzales might retire from the House before he would ever be called upon to vote in a way contradictory to my principles. You could also make the argument that Balart, like many Republicans (ironically many of the same ones who are weak on guns) doesn't really give a hang about abortion.
Still, I feel I have to take a stand on the pro-life issue in some way. I guess this just shows how hypocritical even serious pro-lifers are. The only reason they do not take their beliefs to their natural conclusion is because they fear death or imprisonment. Those who do not unreasonably fear those things do wish to face them alone and thus they choose other issues where they have more friends and the sacrafice they will be called to make is farther away from being demanded. Even then, many of these people will turn about to be nothing but talk.
The pro-choice crowd will win because they have the law on their side and because they genuinely believe that the fetus is not a human being and that they have a right to terminate it.