
So, a lot of people are talking about how brutal, unreasonable, and possibly OOC it was of Daryl to kill Fat Joey, but there's actually a reasonable explanation to all this. And it doesn't involve full measures.The thing is, isolation and torture does terrible things to people. Isolation in particular is a very serious form of torture, and you can read about it here. Alongside degraded brain function– sort of like an atrophied muscle–, sapped concentration, social difficulties and withdrawal, and hallucinations, one of the biggest symptoms is fits of uncontrollable rage. Lashing out, misophonia, unreasonable protectiveness over food and property... Rage with no apparent source. Prisoners punished with solitary tend to just become even more violent. POWs experience ego-dystonic anger problems; the urge to commit violence can be overwhelming. Terry Anderson, a journalist that was held captive and isolated by Hezbollah for seven years, says that he quickly reached a point where he would risk his life by trying to attack guards just because they came too close to his bed. I've read similar things from Holocaust survivors struggling with this even long after liberation, but unfortunately I can't find the article.Something else that happens is dulled ability to interpret other people's emotions. Perhaps this contributed to how Daryl ignored Joey's pleas. His possession of Rick's Python was also a bit incriminating...Now, Daryl wasn't there for very long- two weeks tops?- so it's hard to say how much he was affected. Studies do show that a single week of isolation is enough to affect brainwaves, though. And it is important to consider that he had sensory and sleep deprivation on top of it, which is a whole other ball game, and the fact that Daryl has been through the wringer even before this happened. I simply cannot find the quote, but on Talking Dead, when David Alpert was asked about Daryl's thoughts on Maggie's grave, he said that Daryl was too busy dissociating (when the mind reaches a breaking point and takes a break from reality to protect itself) to really notice what was going on around him. That alone is a pretty serious symptom, so it's not hard to believe that going back to the Sanctuary for even more torture had a huge impact on his psyche.So no. I do not think killing Fat Joey was some kind of proof that Negan influenced Daryl to become more like him, or a measured change in the way Daryl views the sanctity of life in terms of killing Saviors. I think Fat Joey was just in the wrong place at the wrong time.