Episodes 1-3 killed people regardless of whether they were selfish, selfless, good, bad, whatever. The message is that humanity's morality and social contract is now irrelevant because it's unable to deal with the zombie apocalypse.
So, I think episode 4 should start developing what morality means in The Walking Dead and distancing itself from real world morality. I don't want the writers to expect people to feel bad or good about things based on real world morality, but instead based on whether those things are moral in The Walking Dead.
What will the new morality look like? I think it is now moral to mercifully kill someone as soon as they are too weak to continue and to take their stuff. It is moral to take unattended stuff to strengthen yourself and those around you. It is moral to leave people behind if they are wounded and there isn't time to kill them. Giving resources to a dying Duck (for example) is immoral, whereas killing him quickly and mercifully is moral.
I'm curious what people think about honesty. Is honesty still moral?
It seems like morality is whatever keeps you strong ... and keeps others strong, so long as it doesn't endanger you. So ... backstabbing others may or may not be moral based on the situation. Telling the truth so that people trust you and work better with you is moral, but lying to them so that they don't throw you out of the group is also moral. The result, more than the action or intent, determine morality in The Walking Dead.