I wouldn't equate nihilism with sociopathy or megalomania, so you may be barking up the wrong tree there. I'm not even putting Buddhism at arms length in saying that this religion is subversive. On the contrary, I think Buddhist enlightenment is consistent with what I've said about transhumanism and cosmicism. That is, I think there's some overlap between my philosophy and Buddhism.

The question at issue is why an arhat wouldn't outgrow social norms along with egoism. Social laws would be needed to rein in egotists, but also to perpetuate that very egoism via nationalism, anthropocentrism, humanism, imperialism, theocracy, etc.

Again, I'm sure an arhat could be trained like Pavlov's dog to be selfless, but that would be a matter of mechanical causality, not the coherence of Buddhist philosophy.

It doesn't bode well for the standard view of Buddhism if you need to say that the truth here is "beyond mere logic, reasoning and philosophical conjecture. It is an experiential change that results from practice." That's an appeal to mystery that would reduce Buddhism to the level of theistic religions.

If Buddhist practice causes selfless behaviour, I can explain that as I do in the article: this is a defense against the trauma of the nihilism found with the cosmic perspective. The arhat would suffer from cognitive dissonance in being internally conflicted: the residue of the evolved ego would clash with the newfound perspective of neutrality that alienates the arhat from both egoism and social biases (including morality, and the preference for compassion, joy, etc). So the arhat wears a mask of compassion as a bodhisattva, to avoid the insanity that awaits her in pure nirvana.