It's a song and a "comic" song - but reading through it, it strikes me that there's a subversive element running through it, and it's not merely signing up for a "Spare the rod and spoil the child" approach.

Up until the last two verses it comes across, in print anyway, as pretty sceptical about that style of child-rearing. What's achieved by heavy discipline is that:

"Now poor old Bess got so darn mad
She ran away one day
To meet that travelin' salesman...

Which wasn't, I imagine, what was intended.

And even with the last two verses, it is pretty clear that the heavy-handed approach didn't work out as planned.

Moreover, and I'd think maybe this takes a lot of the offensiveness out of it, the moral isn't "Behave yourself, young lady or you'll get slapped" - it's "Be careful not to get caught, and you'll be all right." And the last line seems to imply that Pa is a hypocrite anyway. ("And you won't have to worry, Cause you won't see much of pa.")In fact, read that way, the chorus does the same for the whole self-righteous family:

"Slap her down again pa
Slap her down again
Make her tell us more pa
Tell us where she's been
We don't want our neighbors
Talkin' about our kin
Slap her down again pa,
Slap her down again."