[throwaway290]

> What's so particularly private about the 'inside' of anyone's body

Seriously? If your body is not private to you, then what's so particularly private about your communication?

> I don't agree

That's not an answer to "how would they go about it if their goal was to actually combat child abuse, as opposed to some conspiracy to surveil that you imagine"

> I'm trying to infer what thoughts might exist in another person's head when they do or say certain things

Exactly. It is what you think they think, not what they think, and such says more about your mind than theirs.