> In one of them, Peppa Pig uses a razor blade to slice a piece of her own arm, right after eating her own father.

You mean the one clearly on a channel not officially associated with Peppa Pig's creators and that starts with a fake restricted content warning? Ok, yeah that was dark. But Youtube is not a G-rated site, and it's designed to make content discovery easy.

Doesn't Youtube have parental controls? If that's not enough, maybe there's a need that needs to be filled by a browser plugin that restricts the UI or external player. Either way, letting a child on to Youtube unsupervised is taking the risk of having them stumble across content you don't want them to see.