Imagine the unfortunate child who's been fed peanut butter to only find out it wasn't really butter.

Why?

One of the dairy industry lobbying arms is trying to convince us it's dangerous (e.g. with https://youtu.be/oLjEG8Qu1Qw) but it's bullshit.

Hopefully you were fed human milk. Are you suggesting children are being fed oat milk instead? I don't think you can buy human milk from shops yet so I don't see how this would help with that particular confusion.