He apparently is radically pacifist, in the sense that he doesn't even believe you are morally in the right to defend yourself if your life is being threatened.

Nope, that's not his stance. Any rational person sees that self-defense is morally justified. Molyneux just applies The Non-Aggression Principle to children too. Children are human beings, and so if it's immoral to aggress against human beings, it's immoral to aggress against children too, even if they are your own and being inconvenient to you.

It's kind of strange, but it's also interesting. I think he's anarcho-capitalist in a political sense, I can't remember. Anarcho-something for sure.

Yes, Anarcho-Capitalist. But that's what you become if you apply the NAP consistently, even to tax collection, even though the implication is that governments are immoral (because they threaten us with imprisonment to get money from us, and if we don't pay, their agents aggress against us).

So, feel free to adopt the NAP as a consistent moral principle, and join a relative handful of people in sanity.