I am working on an idea about negative and positive social interactions.
John Gottman, a famous divorce researcher, has argued that in a marriage, negative interactions are so corrosive that you need at least five positive interactions to balance them out - and more than that to keep your marriage in an emotionally positive tone.
Several positive psychologists have said that in our normal social interactions with friends and acquaintances we should have at least three positive interactions for every negative one.
It seems reasonable to me that the least intimate social relationships - the anonymous cash transaction at an unfamiliar store - needs at least ordinary civility on both sides to keep both parties on an even emotional keel.
Which leads me to an idea. Negative interactions are socially corrosive. They are not neutral, but costly to society. People who are consistently negative leave a wake of social costs for other people, and not just the ones they were negative to. It is as if they walked through the social world, dropping acid on others.
Negative people impose costs on other, so more positive people have to salve those wounds with extra positive interactions. The positive people have to make up for the residue of the negative - on top of the normal civility that we need to make sure our own interactions are at least emotionally balanced.