>Why would a child watch a gang bang?

Because they accidentally ran across a link and clicked on it. YouTube comments are filled with links to porn / non age appropriate material for example.

>I worry about vile content targeted toward children.

As do I. But I don't think targeting is necessarily the issue here.

PornHub does target to children though. Their Instagram had a post about children watching porn for example.

>I worry about these things showing up on his youtube feed, not a porn website.

It isn't hard to mistype YouTube and since many pornsites have the word "tube" in them it wouldn't be hard to imagine they could get to a porn site.