I would ask you to try switching the variable and see if the logic still applies. What if your adult child keeps overstepping boundaries? Is it ok to smack them? What about a spouse, or a parent with dementia? Or how about, instead of a child, it was an employee or a coworker? Are these people ok to be hit? Would there be certain circumstances where it's fully appropriate to hit your boss, your grandparent, your wife, etc?

Honest question, btw. Not trolling.
Thanks!