My choosing that quote goes a long way to showing what I think.

Spanking is engaging in violence to someone weaker than you, and shows a failure on the part of the adult. Sometimes a misunderstanding.

It depends on circs. and people as to what's going on.

If you tell a child to do something and they don't, some parents will spank. The child might learn that violence is a solution and believe they are bad. Yet the spank might be that parent wasn't just being obeyed when the parent was fraught or in a rush, and was an expression of their frustration. That's not what the child grasps.

So I think there can be any number of elements in play.

For another take, see Wilhelm Reich's little book, "Listen,Little Man".

Part of his point that we make our own cages as in kowtowing to authority. I think spamking can have a related effect. it creates/reinforces a tendency to look to authority.

Another consequence can be that those spanked, when they grow up, are supportive of punishment rather than restorative justice.

it insensitises everyone and nurtures blaming; who wants to be smacked again?

Idle thoughts of an Idle fellow, Jeri.

Ivor