I can't speak from a parents point of view when it comes to spanking and physical punishment. I have children, but I feel guilty even giving them time outs. I'm a horrible disciplinarian, I'm more apt to laugh at their antics than punish them.
I can speak from experience of being a child beat on a regular basis because some men in Brooklyn told my Father to.
As much as I'd like to think I've totally moved on, and as much as I cringe at the cliche' of "having a bad childhood", I still carry quite a bit of baggage around from all that.
My Dad never told us twice... ever. He told us once and then we were beat. There were times I was given a note to get out of PE because of the bruises from my middle back down to my knees. It still makes me sick to my stomach to think about it.
I won't get into all the horror stories, just suffice to say I still carry the feeling that my Father never loved me. My brothers and I were mearly little robots to be beat into submission. My Father never knew me as a person. The disciplining policy is a big reason for that. My feelings were irrelevant... my obedience was all that mattered. They don't make any effort to understand the psychology of children... just make them fear punishment, and your children will do anything to try to make you happy.
It worked until I was 17, I took the first chance I got to get out. That's the problem with the system... control only works so far.
I don't know if this answers any of your questions... just a bit of rambling on my part. I find it hard to even articulate this stuff... it's pretty buried.