It's pretty clear he never said it was "acceptable." He waffles on whether it should be punishable by death and decides in the end that it must be, but, as one might say today, "that it's pretty fucked up."

The reason is that having an illegitimate child in the eighteenth century was a source of dishonor that would see you effectively rejected from society. So out-of-wedlock mothers were in an impossible situation: kill the child or have their own lives destroyed.

See this article https://www.jstor.org/stable/20484950, which quotes Frederick the Great, among others, who pointed out this same quandry:

> A girl, only too easily fooled by the presence of a seducer, does she not find herself compelled by the very force of circumstances to choose between the loss of her honor and the elimination of the unhappy fruit that she has conceived? Is it not the fault of the laws to place a girl in such a desperate situation?