It sounds like you are working with a bunch of jerks who get their self esteem spikes by treating other people poorly. Most offices have people like this and often times they are in positions of leadership unfortunately.

You said it yourself, these people are not your friends and you are not defined by how they treat you. They are defined by how they treat you. Instead of trying to understand why these people treat you this way, begin understanding why they effect your self worth when you don't even like them or consider them nice people. I know that it may seem I'm making this out to be more simple than it is. I know there must be a lot of emotion behind this for you and I'm sorry. How they treat others is a reflection on their character and not your value.