Unfortunately (I say that as the descendant of Southern Unionist Republicans), the "chrstian abolitionist movement" was not orthodox. It was made up of free-thinkers, Unitarians, Transcendentalists, "free love" advocates, and people who wanted to abolish all "power relationships" (including husband and wife). Naturally such people would go after slavery first before moving on to marriage.
However, this does not mean that one must be a nihilistic freak to oppose slavery. There were perfectly orthodox chrstians who fought against it, such as Wilburforce, Charles G. Finney, and that most right wing of right wing Catholic converts, Orestes Brownson. And the most radical abolitionist of them all (John Brown) was an orthodox Fundamentalist Calvinist.
The irony to all this is that slavery is permitted and regulated by unchanging Divine law (Halakhah), and it is forbidden to add to or take from Divine Law.
“free love” advocates
World Magazine editor Melvin Olasky, historian of 19th century newspapers benefitting from abortion advertising (”menstrual irregularity” cures for women who had failed to menstruate because they were pregnant, in other words, abortifacient “pessaries”), wrote a book.
Titled “Abortion Rites”, it was mainly to refute the claim in another book that English Common Law allowed abortion. Olasky showed that in Revolutionary/Colonial America, when a woman became pregnant, the father was forced into a “shotgun” marriage, and that many of these were perfectly happy.
And Olasky records at least one case in which an aborting woman was executed, during that period.
Olasky related how the “free love” movement was related with the 1840s “spirit rapping” religion, started by the Fox Sisters in about 1843 in Hyde Park, NY, variously called Spiritism or Spiritualism, later debunked by Harry Houdini.
These spirits were real, but they were unclean. Spiritism formed a dirty, hidden motive for the spiritual causes of the Civil War. It wasn’t just the southern proponents of The Peculiar Institution who were responsible for the carnage of the Civil War.
In the North, up to 4 million of the smart-set, the upwardly mobile, were adherents or casual hangers on to the seance religion.
Their religion’s sexual angle taught that it was immoral to bring into the world an unloved child.
Fifty years later, Margaret Sanger was a participant in seances. She, perhaps only coincidentally, was in large measure responsible for bringing this viewpoint to the 1960s, in the phrase
A World full of Wanted Children.
Liberal kooks. That's what I try to tell people, but they want to believe what they want to believe.