Should a parent control a child's hair style?

I have a little brother age 11 and nowadays it is in style for them to have long hair to their shoulders. My mother hates it and threatened to sit him down and zip tie his hands in a barber chair and cut off his hair to a shorter hair cut because she does not like his hair and he refuses to cut it. I told her if she ever did that I will never bring my children around her again because that is some Hitler type shit. Children don't have control over much and see their hair as a part of their identity and you need to respect that. The child isn't an extension of you but rather their own person, and if they know you refuse to respect them and their opinion (something like their hair, we aren't talking about big decisions here) they will hate you now and when they grow up. What do you guys think?