Personally I don't think they think at all. It goes with that entitlement feeling. People just taking what they will, without thinking about what the cost is to someone else. It's a "everyone for themselves" attitude. Unfortunately, it's life. I wish it wasn't.
So, I learned early to take care of myself, WITHOUT stooping to their level. I'm going to have boundaries, no one is going to treat me badly, I am in control over who I LET hurt me. They can only hurt you if YOU LET THEM. I'm also NOT going to be closed, afraid and bitter. Because that will limit my life. No one is worth that sacrifice. I'm still going to love people, I'm still going to give people the benefit of the doubt. I'm just going to be smart about it.