Mr. Hume: The salience of abortion as a social-conservative issue has at least three components:
(1) As an aspect of the culture of permissiveness that persons of a conservative temperament deplore. Abortion “travels” by association with promiscuity, homosexuality, pot smoking, and the rest.
(2) Roe v. Wade as a judicial-usurpation issue.
(3) RC metaphysics (with Evangelicals tagging along for the ride) based on the concept of ensoulment. RC intellectuals throw up big clouds of squid ink here, but the underlying belief is plainly metaphysical. “God ensouled this creature. Abortion thwarts God’s will.”
Number 2 obviously wasn’t in play until 1973. Number 3 only really pushed to the front when RC intellectuals got to critical mass among conservative propagandists, which I think was ca. late 1980s. (I don’t have Damon Linker’s book to hand.) Prior to that, number 1 was pretty much it.
I don’t know how things were in the USA, but the abortion debate in Britain in the 1960s, which I followed closely, was all about class. Middle- and upper-class women could get comfortable abortions with little trouble, everyone knew that. Poor women couldn’t. This was unfair. The counter-view was Nixonian, based on antipathy to “permisiveness.”
The distaste for “permissiveness” in general was not dogmatic or ideological, and conservatives of Nixon’s generation were free to take any legislative position. Margaret Thatcher, for example, voted pro-choice.
And setting aside racial issues, abortion probably does have a eugenic aspect. If intelligence is considerably heritable — and the evidence seems to be that it is — and if it’s disproportionately the left-hand side of the bell curve that’s getting abortions — which seems likely — then abortion is eugenic. That logic seems to account for at least some of the enthusiasm for abortion among the authorities in Communist China, where wellnigh everybody takes eugenic ideas for granted.