As far as I can tell, I can divorce myself from being human while thinking about morality.
Seems to me that if you weren't human, you wouldn't care about morality (and instead care about paperclips or whatever). So even if you try to imagine yourself as some kind of neutral disembodied mind, the fact that this mind is interested in morality (instead of paperclips) shows that it's a human in disguise. Otherwise it would be very difficult to locate morality in the vast set of "things a mind could consider valuable", so there is almost zero probability that the neutral disembodied mind would spend even a few seconds thinking about it.
I dare say that a disembodied, solipsistic mind wouldn't need to think much about morality. But an embodied mind, in a society, competing for resources with other agents, interacting with them in painful and pleasant ways would need something morality-like, some way of regulating interactions and assigning resources. "Social" isn't some tiny speck in mindspace, it's a large chunk.
There seems to be a widespread impression that the metaethics sequence was not very successful as an explanation of Eliezer Yudkowsky's views. It even says so on the wiki. And frankly, I'm puzzled by this... hence the "apparently" in this post's title. When I read the metaethics sequence, it seemed to make perfect sense to me. I can think of a couple things that may have made me different from the average OB/LW reader in this regard: