What made selling out so psychologically vexing was the level of gradation inherent to its principles: It did not simply mean someone was trying to sell something in order to get rich. It meant someone was compromising the values they originally espoused in exchange for something superficial (which was usually money, but not necessarily). This action was particularly bad if the compromised person was still doing the same work they’d done before, except now packaging that work in an attempt to make it palatable to a less discriminating audience.
