I woulnd't say he was right, its one life vs millions, i just dont hate him for doing something wrong.
I understand, I'd say more so that his perception is that he is right.
I think its easy not to hate him as we are separated from the conflict, it doesn't effect us. I feel if all of this personally effected us, like family who died, mothers, daughters, sons etc if we hear the that cure could have been made, but a man stopped it from happening, we would have different takes.
There would be that "what if", that "what if he let them continue and we found a cure and suzy didn't die and got cured etc" and course the very direct, "if he didn't kill our parents in that hospital"etc
So I feel sure, its easy not to hate him as none of us lost any parents or family due to him, thus hard to connect that.
Abby's actions cannot be justified in any sense if she was aware of the circumstances surrounding her father holding someone against their will to experiment on them. It's simply a revenge killing of someone who did nothing wrong.
From her perspective, its for the greater good and someone killed her father, thus is just to her to find that person and do them in.
I'm sorry but...I don't really buy that anyone here is having their parent killed and thinking they will just let it slide or anything odd like that. Look up gangs, do you think they give shit that the reason someone killed their family TO THEM was just? Not really, they will find them, smoke them etc
I don't know of many that will really, like truly be like "wow, I see now, its ok you killed dad and or mom" lol Someone would have to be a saint and with the rage folks have against Abby, a plie of pixels, a fake character, I simply don't believe in real life no one here would seek revenge.
If anything, look up the cases of self defense, to the family that lost a family member, it doesn't matter it was ruled self defense, it doesn't matter that from the person's point of view, they were justified, you'll still hear "he could have walked away, he could have not used a gun, he could have called the cops instead" etc etc
When emotions are up like this, I don't really buy that someone is just doing some dumb game logic and being like "the main character is right, my mom deserved to die bro" I've yet to really see this much in real life, to say that is the norm and that is how humans will behave about something like that.
People generally will not side against their family in this respect.
TLDR - Abby like most humans will rationalize her actions just like Joel rationalized his. They will not side against their own based on logic as humans rarely do.