i kind of get where you are coming from but denying access to knowledge/reality is not helpful.
If that specific video exists and if it's common, this conversation could be had; but, it's relatively uncommon, making it a surprise.
The real answer, as someone else has alluded to, is that YouTube is something that parents should watch or be aware of with their children.
There is a great deal of valuable information on YouTube and cancelling it wholesale is absolutely the wrong approach.
It is common: https://en.wikipedia.org/wiki/Elsagate
Youtube is not something kids can use without supervision.