This is in line with recent game theory studies. In iterated prisoner's dilemma, the introduction of kindness wipes out always-defect strategies in the long run, and is competitive with tit-for-tat.
Doing that will tend to convert tit-for-tatters and might flip other strategies into cooperating. If you grade by the total number of cooperate moves in the group, the group wins by 'kindness' flipping a variety of strategies into cooperate mode. It'll tend to expand pockets of cooperation. No immediate personal benefit, but tends to make the environment better which may seem like a benefit.
I don't think 'survival of the fittest' has to mean 'kneecap all your opponents and rent-seek', but that's the popular interpretation in Western capitalism :)