Occasionally I meet people who are not serial killers, but who have decided for some reason that they ought to be only selfish, and therefore, should reject their own preference that other people be happy rather than sad. I wish I knew what sort of cognitive history leads into this state of mind. Ayn Rand?

As far as Rand goes, this is a common but inaccurate characterization of her. From reading her fiction, it's clear that the heroes derive enormous benefits from each other - emotional benefits, not just monetary. She certainly didn't advocate that people reject their preference that people should be happy rather than sad. In fact, what she advocated was something similar to this post - that morality is not an external burden but something that's part of you.