It is always easy to justify non-cooperation. The demo even provides one by showing that partial non-cooperation provide the greatest economic benefit. If the benefit was measured differently, say in terms of character, then the conclusion might be different. Or to put it another way, economic gain may or may not be the best way to decide if cheating is ok.
I mean one of the premises of the simulations is killing off the poor to make room for the rich. Accepting, based on the simulation, that partial non-cooperation strategies are ok means accepting that premise.
And so I've grown tired of reaching out to people. There simply have been too many let downs. I mean I don't even expect people to return favors. It's just hard to see "friendships" end abruptly after, say, 2 years just because the other person changes his/her set of goals. In other words, you learn that all the times you had fun together you actually never had a friend.
I wonder whether this kind of behavior has become more prevalent in recent years. I'd like to believe that 10 years ago I was better at seeing through people. But these days? It feels like many people have got the pretending of being genuinely nice down to a fine art.