Earlier quoted context omitted.
I think that there's an element of validation and indoctrination that is a serious concern here. In addition to an overall significant lowering of the discourse around things by allowing garbage quality trolls and other horrible comments, and in addition to bullying, aggressive behavior, stalking, and other things that are broadly considered unpleasant, this kind of behavior breeds more of this behavior. Consider som…
I think there is no evidence of the mechanisms you describe. That could have been a text written about books shortly after Gutenberg. The kids will flee the garden eventually anyway and "allowable discourse" is quite subjective. You will never create a child-proof youtube. Those kids will eclipse your abilities and understanding at some point. It would be better to create a separate platform
From usenet to reddit, many communities that tolerate abusive conduct degenerate, as the "bad behaviour" is normalized and becomes accepted.
The fact that you can't create a child-proof YT doesn't mean you shouldn't strive to keep negative behaviour at bay.