I think what Joel did was selfish in any other perspective, but from his perspective it's just what any parent would do. Abby has trauma but only the nightmares of her father's death, but not of that defenceless old man, she tortured and murdered imhumanly strangely enough. Abby see's Ellie that Ellie has just killed her pregnant friend, gets pissed off, but then tries to kill Ellie's pregnant friend? Bit hypocritical if you ask me. And to say that Abby isn't normally the type to slit a pregnant woman's throat, but she'll torture and kill an old man who just saved her life while his daughter watches and begs her to stop. Just doesn't add up for me.