On the other hand, I don’t think having the opinion that you should wait until 18 is that abhorrent. I disagree with it, sure, but it’s not an extreme opinion.
One thing I’ve always noticed with folks who seem to misunderstand trans issues is they always liken gender affirmation surgery to “cutting/chopping off a boy’s penis” because in their head the loss of manhood is the worst thing that could ever happen. It’s never about the opposite scenario.