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It's what i want say. He got too much pain from his expierience. He have moral, and it make him soooo fucked up or other people even he didn't have any malice.... he killed a lot of people or watch destory society because of him or his granpa. I think, morty try to run away from all those pains, but he came back by himself.
Spoilers for “Rest and Ricklaxation” below:
Morty losing his capacity for empathy in the detoxifier makes perfect sense considering how often he’s watched worlds get destroyed and people getting killed. And considering how often his ideas of what it means to be good or bad have been called into question. Even if he maintains his beliefs that there are ways to be a “good person”, he knows that trying to put those beliefs into practice has caused him nothing but trouble, and people are going to die no matter what he does. Or sometimes because of what he does.
How often does this mean Morty’s wished his ingrained morals away? How many times has he hurt for somebody else when he was powerless to help, and just wanted to cut that part of his heart out? It’s no wonder his psychological detox turned him into, as Toxic Rick said, a psychopath.