Somewhere before "actively recommending people feed their kids poison," I should hope.
1. Kids are unable to defend themselves from their parents, especially ones that need additional care.
2. Forcing kids to drink poison constitutes child abuse.
3. YouTube should not recommend videos which advocate for child abuse.
It seems like every time there's parents doing something that constitutes literal child abuse as a result of incredibly dangerous videos, there comes people more concerned about the slippery slope logical fallacy than the parents committing child abuse and the people perpetuating it.
Incidentally, the most effective and least abstract arguments against murder and genocide are based on emotions — leaving them aside, you're left with assigning a worth to the lives taken.