Murphy is such a great character. The writers go out of their way to make sure he is completely unsympathetic. This is the episode where we see Murphy become part of the group rather than the goal of the group - whether because he has a thing for Warren or because he knows he needs them to get to the CDC to get help is left ambiguous - and it could have been the beginning of a sort of redemption arc, a “he’s not so bad after all” story line.
Except that he gets the food and water for the others by stealing it from a woman and her young daughter. Then, completely unnecessarily, he lets a zombie in to eat them. This is not a guy you can like or respect. He’s a great character.