The people frightened of intelligence explosion are worried about something like an AI version of existentialism: a mind that accepts some moral system without even trying to justify it, and then optimizes accordingly. It's certainly possible to just accept as axiomatic ethical standards which don't come from any intrinsic feature of the world.
I've seen lots of essays (not this one) claim that morality will "inherently" emerge from intelligence, which I think is absurd. Shit, my moral views aren't an 'inherent' product of anything except my evolution-shaped brain that feels empathy.
That's where I think "AI won't be like humans so it's fine!" essays screw up so catastrophically; "not like humans" is exactly what people are worried about.