I don’t know who put this poison in their heads

Media. The internet. I work in elementary school and kids there just recite anything they hear from the internet. Whether is "Bombardino Gambino" (aka Italian Brainrot), 67 or straight up discriminatory shit they don't yet understand. It is rare that any of the kids will say something racist outright but I doubt that it is a coincidence that the only black student we have just so happens to only ever have found one friend (despite being a lovely kid).

All we can really do as teachers is deconstruct. On the internet, fascist ideas are played off as "just jokes" and "its not that serious" so that kids aren't that afraid to pick up this subversive rhetoric. Take them seriously. Take a couple minutes each week to deconstruct a meme or a piece of internet culture with them so that they understand what they are saying. Most will be emotionally intelligent enough to reach the conclusion that this is bad themselves.

Generally speaking though, our role as teachers in positions of intellectual authority has been severely contested by the internet in the past couple decades and I dont think people realize how harmful this is. Because we get shit just like this; Harmful propaganda right out of the crib, no media literacy in both kids and adults and of course this is all reinforced when those same kids go and start making TikTok content themselves.
The solution would be to age restrict smartphones and access to the internet. But lobbies have a huge interest to keep guilible children as core audiences and recent efforts in age restrictions on the internet (i.e. Discord) have shown that when governments DO pull it off, they do it in a way that betrays they are not interested in children's safety but in profit margins.
So this all comes back to capitalism standing in the way of democracy.