Taking this to another direction....spanking
I don't think Petty was minimizing the trauma for the girl, but more talking about from a guy's perspective it doesn't look as intense as things like being beaten up on camera, etc. For a guy, getting your head shaved is definitely not as traumatic. I think it was over the top for the father to do that, but also think there were underlying issues driving her beyond the haircut. Women throughout history have had to endure head shaving as some sort of "ultimate punishment". In disciplining a child, I think the key is not acting in anger, so that you're teaching the child, not simply retaliating.