"A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses."
Because gains/losses can be hard to quantify. Punishing people who violate rules of fairness is a useful strategy proven by game theory ("Tit for tat"), and there are indications it is a deeply ingrained human behaviour.
You might argue that even when it incurs losses to the punishers, its overall gains outweigh that, but those are future, hypothetical gains.
What about other cases where such future, hypothetical gains are less well-founded, but still expected by the "stupid person"? What about emotional gains?
It's not as easy to draw lines here as it may seem.
"A stupid person is a person who causes losses to another person or to a group of persons while himself deriving no gain and even possibly incurring losses."
Because gains/losses can be hard to quantify. Punishing people who violate rules of fairness is a useful strategy proven by game theory ("Tit for tat"), and there are indications it is a deeply ingrained human behaviour.
You might argue that even when it incurs losses to the punishers, its overall gains outweigh that, but those are future, hypothetical gains.
What about other cases where such future, hypothetical gains are less well-founded, but still expected by the "stupid person"? What about emotional gains?
It's not as easy to draw lines here as it may seem.