“If you’re genuinely selfish, then why do you want me to be selfish too? Doesn’t that make you concerned for my welfare? Shouldn’t you be trying to persuade me to be more altruistic, so you can exploit me?”
You’re conflating selfishness with vulgar egoism. Suppose your well-being makes me happy, and I believe that making you selfish will make you happier. Then convincing you to be selfish is the self-interested thing to do. If I tried to convince you to be more altruistic (in the self-sacrificing sense, not in the benevolent sense) so I could exploit you more, that would be bad for you, which outweighs the benefit I’d get from exploiting you. Selfishness is about maximizing your hedons, which does not at all imply not caring about others—in fact, it usually means caring for some others.
You’re conflating selfishness with vulgar egoism. Suppose your well-being makes me happy, and I believe that making you selfish will make you happier. Then convincing you to be selfish is the self-interested thing to do. If I tried to convince you to be more altruistic (in the self-sacrificing sense, not in the benevolent sense) so I could exploit you more, that would be bad for you, which outweighs the benefit I’d get from exploiting you. Selfishness is about maximizing your hedons, which does not at all imply not caring about others—in fact, it usually means caring for some others.