We don't allow teens to do many stuff due to them not having their brains developed well enough thus being the equivalent of retarded adults. Self mutilation shouldn't be an exception because socipaths said so.

"Oh but some teens develop faster", well we still don't allow 14 years olds to drive just because little Timmy drives the family truck around the farm since he was 12 or Dorothy to buy guns because she's been around firing ranges since 9.