I reject the idea of a deliberate conspiracy to discredit rational self-interest. Instead, I suspect most people simply don’t consciously connect the word “selfish” to its root. The word’s negative connotations may simply have arisen over time. Two hundred years from now, most people may not know that “pimp” originally meant a man who exploits prostitutes for financial gain.
I am not talking about any conspiracy, but a philosophical movement. In fact, not even a movement, but an idea, the idea of altruism. Philosophers and religious leaders from all sorts of traditions have promoted altruism as a moral ideal, and denounced self-interest as evil. See the post in which I quoted from Ayn Rand’s Introduction to The Virtue of Selfishness.