Okay, how about this. This requirement for age verification is because someone is asserting that profanity or whatever youtube decides is "adult only" is harmful to children.

Since you can't prove a negative, e.g. profanity isn't harmful to children, the question here is can you prove profanity harms children. Yes anecdotes aren't evidence, but what can be asserted without evidence (profanity is harmful) can be dismissed without evidence.