>> The higher that niceness exists in the social order, the greater its contemporary benefit

Could also be said that the more niceness, the more likely that not-nice actors will violently overthrow the nice ones.

As an example, we have had numerous bee hives at our place. The bees that never mess with us when we come near their hives are more likely to get robbed by another hive and destroyed. The bees that would sting us when we came near were rock solid - they never got robbed or collapsed.