Daily reminder that the internet doesn't absolve you of actually parenting your kids, and keeping and eye on what they browse on the internet. This isn't unique to Youtube, there are all sorts of bad places kids can end up if left alone on the web.
The problem we have is determining what is good content and what is bad content and who is the arbiter of what is good or bad. Something you think is bad, might be something someone else thinks is good. These determinations are highly subjective.
Youtube has some culpability here.