Because individuals who believed “don’t take advantage of others” were at evolutional disadvantage comparing to those who believed “do not get taken advantage of”, and thus did not procreate and died out
Like first ones would just get taken advantage of all the time, burn out and die miserably.
Second ones would preserve their mental health and be able to achieve anything meaningful like raising kids.
Do not listen to what people tell you but watch what they do. If society did not tolerate sociopaths, sociopaths wouldn’t govern nations and own multi-billion dollar corporations. This behaviour is not only accepted but encouraged.
By the way I am feeling depressed rn so that’s why I am being so pessimistic, do not take too seriously