I'm reading Ayn Rand's "The Virtue of Selfishness" and it seems to me that (a part of) what she tried to say was approximately this:

Some ethical systems put false dichotomy between "doing what one wants" and "helping other people". And then they derive an 'ethical' conclusion that "doing what one wants" is evil, and "helping other people" is good, by definition. Which is nonsense. Also, humans can't psychologically completely abstain from "doing what they want" part (even after removing "helping other people" from it), but instead of realising the nonsense of such ethics, they feel guilty, which makes them easier to control.

I don't read philosophy, so I can't tell if someone has said it exactly like this, but it seems to me that this is not a strawman. At least it seems to me that I have heard such ideas floating around, although not expressed this clearly. (Maybe it's not exactly what the original philosopher said; maybe it's just a popular simplification.) There is the unspoken assumption that when people "do what they want", that does not include caring about others; that people must be forced into pro-social behavior... and the person who says this usually suggests that some group they identify with should be given power over the evil humans to force them into doing good.

And somehow people never realize the paradox of where does the "wanting to do what seemingly no one wants to" come from. I mean, if no one really cared about X, then no one would be concerned that no one cares about X, right? If nobody cares about sorting pebbles, then nobody feels that we should create some mechanisms to force people to sort pebbles because otherwise, oh the horrors, the pebbles wouldn't be sorted properly. So what; the pebbles won't be sorted, no one cares. But we care about people in need not getting help. So that desire obviously comes from us. Therefore acting on that desire is not contradictory to "doing what we want", because that's a part of what we want.

So... now these are my thoughts, not Rand's... one possible interpretation is that the people who created these systems of ethics actually were psychopaths. They really didn't feel any desire to help other people. But they probably understood that other people will reward them for creating ideas about how to help others. Probably because they understood on intelectual level that without some degree of cooperation, the society would fall apart, which would be against their interest. So they approached it like a game theory problem: no one really cares about other people, but blah blah blah iterated prisonner's dilemma or something, therefore people should act contrary to their instincts and actually help each other. And because these psychopaths were charming people, others believed their theories expressed the highest wisdom and benevolence, and felt guilty for not seeings things so clearly. (Imagine less intelligent professor Quirrell suffering from typical mind fallacy, designing rules for a society composed of his clones.)