Originally Posted by
Revolutionary_Jack
Ellie was a stranger to him. She's not his biological daughter. Over the course of his trip, he grew to care for her and love her, which nobody entirely expected. So Joel intervened to save someone who wasn't his child.
But then what reason is there for anyone to accept he was worth mourning?
We see this doctor from Abby's POV. Abby is introduced to us at that point, as Joel's future assassin. So we can't count on sympathy or emotional connection (I.e. significant to character we like) so we need rational reasons to accept that. The first one this game gives is, he's nice to animals, which okay seems to do the trick for some people. But for others, you need something concrete for us to accept this character. The game gives us nothing. Presenting him as someone who is ready to kill Ellie without a second thought, as someone who had to talk Marlene into doing it, and who, very cowardly, dodges the question of what he'd do if Abby were under the knife...condemns him and by extension, condemns Abby.
If they knew and understood why Joel did what he did, and that they'd do what he did in his shoes, then the excessive anger they display cannot be accepted. If it was a real tragedy, a real miscommunicaton, like the Fireflies forcing the doctor, against his wishes, to operate by putting a gun on Abby, then that I think would have got it around. There you have a sense that Joel was right but tragic circumstances had him kill an innocent person who was himself trapped and that would underscore the theme of the "futility of revenge".