Yes, there is. I can understand giving a small child a well timed swat on the butt, or an older child a number of swats on the posterior while turned over a knee. I understand the reflexive swat, followed by the kid howling for a couple of minutes. This has been a part of human society since the dawn of history.
What I don't understand is the parent who lashes out in anger, and who keeps hitting the child over and over again. I simply do not have any patience for parents who strike out in anger. I don't understand any need for a spanking to last more than a couple of minutes, at most.
Anything beyond that, and as far as I'm concerned the parent is out of bounds. If the punishment escalates to where closed fists are used, or implements are used to bludgeon the child, or blood is drawn, then at that point I'm comfortable with the idea of getting authorities involved.