With all the child-friendly content available on Netflix, Hulu, and HBO (the home of Seaseme Street), I think I'm going to skip youtube until my son is older.
I have been pretty selective with Netflix shows because some of them seem pretty repetitive. I had high hopes for Word Party ( http://nypost.com/2015/07/01/netflix-to-stream-kids-word-par... ) when I first heard about it but it is honestly the same 3-4 songs repeated over and over in each episode. Instead we prefer to let him watch shows for slightly older kids that involve better story-telling and more complex concepts. E.g. We Bare Bears in Hulu is great.
I've noticed that 2d animation content is often much better than 3d and I think the medium post corroborates it.
Probably not a threat, but Youtube channels are really only protected by the strength of their owners accounts.
For netflix et al, not only is the content curated, the content is created by known companies.
For at least 6 months we have forbidden our 3 year old to watch YouTube because he ended up at some (harmless, but totally braindead) Spiderman nursery rhyme video and I figured he would be caught by bad algorithms.
Sometimes the 7 year old wants to be nice to his brother and searches for spiderman. He knows they shouldn't watch violent stuff, but it feels like a drug somehow to watch autogenerated content at all.
I'm a child of the 80's, and many of the cartoons I watched still hadn't been censored of their racist imagery.
I don't believe it harmed me, though oddly enough when I play Cuphead, I do occasionally expect a caricature of someone in blackface or stereotypical japanese to show up, simply because the game shares it's art style with Max Fleischer era cartoons.
That's very hard to know though. We all have unconscious stereotypes.