Super hot take: the reason you could historically tell a lot about a person by how they treat the powerless is that society historically gave permission to mistreat the powerless, so treating them nicely was revealing. Society currently gives permission to mistreat the powerful.
You can tell a lot about a person by how they treat the people they’re given permission to treat poorly.
When you see someone displaying truly nasty behavior toward the people they’ve been given permission to treat poorly, I think it tells you exactly the same thing it would have told you about them were they doing it to the powerless 100 years ago. It’s all about permission.
Note: I am NOT saying that the powerful and the powerless are the same or that mistreating them is exactly the same. I’m saying that how someone treats the people they’ve been given permission to mistreat (whoever that is) tells you something useful about that person.