I think you are all neglecting the events that lead up to this moment with Don, his wife, and the boy in that bedroom. First of all, the wife is responsible for endangering the entire group the moment she allowed that kid to enter that house. Clearly the boy was being chased and that house was not well protected. If they had not let the boy in to the house, only the boy would have died, by letting him in they doomed him and everyone else in that house. Second, when they were in the bedroom the wife chose not to escape with Don and instead stay and defend this random kid. If you pay attention you will notice that 3 zombies entered the room, not just 1. Thus Don realistically could not have fought off all those zombies, plus the countless others who would have arrived seconds later, and save all their lives.
To me, it depends on what your goals are. If your plan is to simply survive, then he made the right choice.
My goal would be the preservation of the living and the extermination of the dead. Therefore, I would do everything in my power to save my wife and the child. I wouldn't go anywhere without a weapon, either. However, should ten zombies come between us, obviously there would be nothing I could do. I would be throwing my life away along with hers. It would crush me, but it would also allow me to keep working toward my goal in her memory. Does that make me evil? I don't think so.
ok not only was he not wrong . he told her to leave the boy , she did not , he was sorry (he said so to her the children and her again) but lets not gloss over they wer traped it was ither both or the one who had a path of escape . and not to be a pourer on of salt but later when she and he wer both saved she took a most selfish act and infected him case closed!