Humankind. :-)
And I don't get to do anything other than dictate my own behavior, and try to express an idea. Sorry if that came off as dictatorial.
What I meant to say was: Anyone who would rather treat someone how they personally want them to be treated, rather than how the other person wishes to be treated, has forgotten The Golden Rule: https://en.wikipedia.org/wiki/Golden_Rule
In terms of human relations in general, and in a very extreme sense, it's the social contract that allows people to co-exist without killing each other. Would you like someone to murder you because you insulted them? If not, it's best to treat people in the same way, that is, not murder them because they insult you. Or, perhaps, just not insult each other, lest you murder each other. But the point is you're caring about how the other person responds to what you do, because that may affect you at some point.
On a purely empathetic level, treating someone how they wish to be treated makes them feel better. That has a lot of benefits, for you and for them. And it basically doesn't cost you anything, other than the extra second it takes to be mindful of how you're treating someone.
And in general people who only think of themselves are selfish dicks. I certainly can't dictate to anyone not to be a dick. But it's in their interest not to be a dick.