When a father inflicts that kind of harm on a child, the generous interpretation is that he meant well but just went too far. The more realistic interpretation (IMO) is that he has temper issues and lost his temper with his son (not too dissimilar from Rice losing control with his fiancee).

Further, there are now allegations of Peterson abusing another of his children about a year ago. These are just allegations at this point, so I don't want to make too much of them. But if true, it suggests a pattern of abuse that makes it even harder to justify the "he had good intentions and was just trying to discipline his son" argument and makes the "he has anger/temper issues and abuses innocent children when he loses control" much more plausible.