Fighting the hypothetical?

With respect to Eduardo's recent question:

Let's assume for the sake of argument that the actual numbers of abortions under a system of legal prohibition would not drop significantly but would simply move underground . . . .  Let's also assume that these proposals by the Democrats would cause a substantial drop in the actual number of abortions.  Setting aside questions concerning the morality of contraception . . . , would that be a reason to favor the Democratic position on abortion over the Republican position? 

In my response, I don't think that I -- in Eduardo's words -- decided to fight the hypothetical.  Instead, I think I responded to Eduardo's other question:   "[I]f you favor the Republican position, is it because you think the assumptions are implausible or is it for some other reason?"  As I tried to explain, I do think the assumptions are implausible.

In any event, though, Eduardo invites us, again, to consider a "fairly narrow question about morality and law," namely, whether "abortion must be illegal, irrespective of the consequences of that prohibition."

Now, Eduardo and I (and Murray and St. Thomas!) agree that not all immoral conduct need be, or should be, illegal.  It is immoral, I assume, to relish in one's mind delicious revenge against one's enemies, but only a monstrous legal regime would make such relishing illegal.  It is wrong to engage in cruel and hateful speech, but we do not -- and should not -- outlaw such speech.  It is wrong to cheat on one's spouse, but no one should go to jail for it.  And so on.

Eduardo and I agree that abortion is immoral.  So, should it be illegal?  Or, to refine the question slightly, "how important is it that abortion be illegal, if its incidence can be reduced substantially by means other than regulation"?

For starters, I have to say that Roe and Casey should be opposed, and overruled -- that is, it should be, again, permissible to regulate abortion -- for reasons independent of abortion's immorality.  They are bad constitutional law, and the fact that these mistakes are more likely to be fixed (though, obviously, not certain to be fixed) by judges appointed by Republicans is a strong reason to prefer Republicans.  That said . . .

I tend to think that it is not enough (though it is a very good thing!) to reduce the number of abortions, while maintaining a legal regime that permits -- let alone funds and constitutionalizes -- it.  Conceding that there are real and important limits to legal moralism, it does seem to me that for a political community to fail to protect innocent unborn children from lethal violence -- that is, to single them out for non-protection -- on the ground that to protect them would violate adults' liberty to "define one’s own concept of existence, of the universe, and of the mystery of human life" is to choose, in a fundamental, defacing, and corrupting way, injustice over justice.  So, I'm hesitant to frame the task of choosing between the two parties' approaches solely in terms of the approaches' predicted effects on the number of abortions.  (This is not to say, I think, the consequences of prohibition are irrelevant to the "should we regulate?" question.)