Well, for one thing, it's more common for a heterosexual couple to practice sodomy than it is for a man to get pregnant. Well, yes, but sodomy laws would invariably be selectively enforced according to existing unjust social standards, and being clapped in irons is more obviously an infringement on liberty than not being permitted to terminate a pregnancy (assuming the mother isn't forced to actually raise the child, which nobody sane is suggesting). Again, though, I could very easily see arguments to the contrary that would be perfectly respectable and reasonable law. (I could also see an argument that strict abortion laws would in practice be discriminatory on the basis of class since they'd be enforced much more stringently and enthusiastically against poor people.)
This is exactly why I'm leery of the 'compelling government interest' model, although I have no idea what I'd like to see it replaced with. Every possible alternative is just as subjective and susceptible to abuse and hackishness as 'compelling government interest' is. Either way you slice it, you're making subjective moral judgments about which acts do and do not rise to the level of calling for government disapprobation and intervention when you invoke this type of scrutiny (how this works with abortion cases is obvious enough, and incendiary enough, that I don't want to spell it out, so instead I'll use
Moore v. East Cleveland, which is my own preferred example of a case where I'm uncomfortable leaving substantive due process in the dust because the conclusion is morally imperative to reach but difficult to reach on other grounds: It's just as much a subjective moral argument to say that extended family members are still family and deserve the right to live together as it is to say that those relationships shouldn't be morally or legally significant). Obviously
something above rational basis review has to exist, but I really don't know how to go about that without abuse and hackishness.
I'd love to agree with this, but my overall political philosophy is different enough from classical liberalism that any set of legal principles that I'd find convincing or morally operative would have to differ from any reasonable interpretation of plain or original meaning in significant ways. My main interest is in making those differences more consistent and giving them a sounder theoretical basis than conventional American liberal jurisprudence (don't even get me started on 'penumbra' bullsh**t).