We're Not Garbage!!!

Today I met a cat. She was a very cute cat, but she was very skinny... when I pet her I could feel all of her bones and her belly was bloated from hunger. My new kitty friend does not have a home.
I don't understand how people can just throw a cat out in the cold and leave it to fend for itself. I always try and come up with an image of what kind of person it would have to be... a person who throws a living thing away like it's garbage. I never manage to picture anything.
I've been thrown away too.
By friends. By family. By lovers.
What is this mentality? Where does it come from? We're not garbage! Stop treating us like we are!