I think you two are talking about different parenting methods.
Parents who hit their young children because they are angry or helpless or parents who physically discipline their children because they want to give them a learning experience. Similar to when a master in martial arts gives his student a blow with a stick on the back, showing him that he should not fall asleep during the exercise, for example.

I would say, however, that woelfchen is referring to parents who are incapable of feeling any benevolent intention behind their disciplining. Those who raise their hands in anger at a young child because they are full of fury will not discipline their child but will confuse it because it will not understand the intention behind the action and will experience it as gratuitous punishment.

A child who does not understand that it was his action and not his person as a whole will later himself have difficulty distinguishing between discipline and arbitrary punishment.

Children, however, can very well sense whether the father or mother is acting out the corporal punishment as a helpless act of their own lack of self-confidence or whether they are exuding confidence. I would guess that the former is far more common. It is a very fine line between parental anger or helplessness and parental benevolence. If you can't walk that line and you don't have self-reflection at the moment of discipline, you are harming yourself, and as a consequence, also your child.

It's very easy to spot because when you have a hitting father, for example, like in my family, his rage will be followed by a very strong guilt trip and he will either beg for forgiveness in front of his wife (for hitting the children) or will indirectly plead for forgiveness in front of the children by falling right into the other direction and fulfill the childs demand or wish for something.

Though how damaged or harmed a child will be in adult life depends on the person him or herself. Since no childhood is perfect it will be everyones own responsibility to come to terms with oneself.

I, as a young adult, was very stubborn towards older people who tried to discipline me and thought nothing of them, oftentimes I didn't respect them and thought they would just want to punish or boss me around for their own pleasure or advantage. I was not very good at distinguishing between benevolence and malevolence and threw it into one pot. This happens a lot to children which were beaten up or were witnesses of their siblings being beaten up "for no reason" (a correct perception when a father or mother forgets him or herself).