Just making a comparison between altruism and tolerance. It works amazingly well if everyone is altruistic, but irl that will never happen. There will always be hawks that take advantage of the fact that everyone else is altruistic. In doing so, hawks become the winning strategy and beat out the green beards. They rise to dominance and at the end everyone is worse off. The answer proposed in game theory (or more accurately, one of many) is a strategy called "Tit-for-tat". Essentially, be an altruist until you're met with hawk behavior, and then stop being altruistic to the hawk. I thought that was very similar to tolerance. It benefits everyone, so long as they are also tolerant but gets easily destroyed by intolerance. I don't care too much about the comparison itself, but most social exchanges can be better understood though game theory.