There is a huge difference between corporal punishment and assaulting a child. With that in mind, parents should and need to administer corporal punishment towards their child, as it is a form of enforcing respect in younger children, which then leads to less drastic punishments as the child gets older. When children get older they do what their parents tell them out of respect and fear, but not out of a fear of being physically punished, rather a fear of letting their parents down. This is why after they get to a certain age, if corporal punishment was used, punishments such as taking away toys (computers, game consoles, phones social activities with friends) and making them do things they do not like such as doing chores etc work because while although the child does not want to do it, they do not want to make their parents more mad than they already are. It becomes more of a voluntary thing out of respect.
In my opinion as I was raised, a slap on the face is reserved for talking back, or talking in a disrespectful manner, swearing continuously after being told not to was grounds for having "non antibacterial" soap put in your mouth, hold it for some time, then spit it out and wash your mouth out (it still leaves a nasty taste but you don't ingest it). Every other offense was ground for either verbal scolding or a good old fashioned ass spanking. None of that is child abuse as long as the severity of the punishment is in moderation.
Parents should be able to do this to their kids, and parents that don't should be beaten themselves for not giving their little shits what they deserve. Most children today need a good old fashioned ass spanking to put them in line and a lot better parenting. To many parents here in the US let their kids do whatever the fuck they want, which is why they turn into criminals or disrespectful arrogant cunts.