Happy is the one who will seize and dash your infants against the rock!”
What exactly is this referring to?
Not to try to pick a bone, but it is unfair to judge moral issues with a twenty first century understanding of moral law matters which occurred 2500 to 5000 years ago.
As it has been said elsewhere many times, the Hebrew statement of “Thou shalt not kill” is not a word for word translation; more accurately it should be “Thou shalt not kill an innocent person”.
The world of the Israelites was a tumultuous one with enemies surrounding them, and battles and wars pretty much a guaranteed fact of existence. God promised them the land, and others who had been occupying it for decades if not centuries had an opinion that the Israelites were invaders; and subsequent to the Israelites establishing the land as theirs, other tribes sought to capture or recapture that land.
As time passed on, it was clear that enemies of Israel once defeated did not remain so; and the concept that every person, including children and women were enemies - those kids would grow up hearing stories of their enemy Israel and the “evil” (perceived) done to the tribe - thus setting up the next round of attacks and wars.
We have now the history of the Israelites to meditate upon, as well as the last two thousand years and the revelation which 0Christ gave us to reflect upon and to further refine our understanding of moral law. Intentionally kiulling the children of our enemies is certainly now not condoned. But we have the 2500 to 5000 years of history, plus the revelation of Christ - which they did not have.
The Church is contextualist in reading Scripture, not literalist. And the context of moral law
One also needs to keep in mind that while other passages in the OT may speak of every last person in a family/group/area was wiped out, that may be literally true, it may have an overlay of hyperbole. Presuming that it is always literally just as written may well be over-reaching.