I figure as a parent its your choice on how you choose to discipline them. I do disagree with your statements that ...
(Parent's who don't spank have perfect children) I have a 4 year old and a almost 17 year old. Perfect...no. Good...yes. My son doesn't smoke, drink, do drugs. He gets good grades (A and B's) Does not get in trouble in school, never in a fight. Yes, he is a pain in the *** teenager sometimes but he is a good kid.
I could say...Parent's who spank have kids who get in fights, exhibit violent tendency's , resist authority. Its what I observe but I don't want to stereotype.
(Parent's who don't spank are more concerned about being friends with their children rather than parents.) Not true. I always made it clear to my children that though I will listen to there side I will be first on the side of the teacher or other authority. My daughter (4) is always telling me that I am her best friend and I Always remind her that we can be friendly but she IS NOT my friend, I am her Mother. I find Time out and explaining what not to do to be much more affective for a young child. With my son, telling him once was usually enough...my daughter, well, that's a different story.
(Parent's who don't spank have very young children and haven't been put in that situation yet) Like I said 16 and 4.
I remember when my son was 8 and my father asked when I was going to start spanking. He warned I would have trouble if I didn't. We were always spanked as were my 2 stepbrothers. I asked him if he still had trouble with the boys (then young teenagers) and he said "yes, all the time" They get in fights in school, troublemakers. So, it doesn't work for everyone.
Each kid is different but I do believe that spanking does teach violence. My daughters teachers tell me that she is the little mother, stopping others in preschool from hitting, pushing or yelling. She tells them that hitting is wrong. And it is.
But then again, that is just my opinion!