There are many shortcuts to ascertaning someone's character. My grandmother was a big fan of the "pinkie ring" school of man signals. (Hint: Men who wear jewelry are insecure and a little bit lavender, per Grandma.) Men tend to like the hard-to-get woman, according to folklore, because no man wants a woman who's "easy." But there's one I go by that applies to everyone.
How they treat people they don't have to be nice to.
"Nice" is a put upon word, often evoked by the bystander neighbors who have belately found out the "nice" young man next door has been stashing dismembered prostitutes in momma's basement. But "nice" is also a valuable word, no matter how many times a psychopath uses it to fool others. "Nice" is what we all should strive to be. Because without a generous helping of "nice," the world as we know it would cease to exist.
That's why I am such of fan of clear moral directives disseminated by every possible authoritarian source. When hate speech, such as so frequently spouted by Ann Coulter and her ilk, are allowed to become a winked-at source for behavior, we all lose. Because there is no end in sight. It's easy to hate our enemies, but that leads to atrocities. We have to be "nice."
We have to be good to those we have no reason to be good to.
Because that's the essence of humanity, isn't it? What makes a person human is debated roundly by many philosophers, but in daily life it comes down to knowing it when you see it. Letting the person with one item ahead of you who have more items. Acknowledging competing points of view and looking for common ground. Recognizing humanity even when it doesn't take a form exactly like you.
Empathy, in short. Maybe you've led a life of exceptional privilege and ease, or have come to that point from a different state. You don't have to be someone who is struggling with identity issues, or poverty, or just a pile of recent bad luck. No one is so privileged that they were not once behind the eight ball, no matter in how small a way that turned out to be. Empathy is the ability to imagine across gender, social, monetary, or circumstantial divides. To realize, "there but for the grace of God, go I." And then, in a great act of humanity, treat that person the way we would want to be treated.
It's the mark of being a good person.
It's the insecure person who takes advantage of a situation and takes more than they are entitled to, because they don't want to ever think that they would be in a positition where they must depend on the kindness of strangers. They don't trust the kindness of strangers because they know they would extend no kindness to anyone they don't have to.
Their world is raw power, and they enforce it.
And that is simply wrong. They are not acknowledging the kindnesses that got them where they are. They'd like to think there were none. That gives them a world where everything is under their control. And there is no such world.
So mark them out. Where ever you may be. Call them on it. Let them feel the withering heat of humanity's expression.
Because the dignity you save, may, one day, be your own.