I don't want to be friends with people I've dated
Some people consider continuing friendship to be a very important part of their relationship, do you not feel this way?
Friends only get in the way
It is okay if you don't want to be friends with people you have dated. If you forced yourself to be friendly with people you weren't comfortable around that would not make for a healthy relationship.
I just want to trash them.
It's okay if you don't want to be friends with former lovers, and you just want to start over without them.  However, you shouldn't be wishing harm on these people, even if it is just in your mind.  They really haven't done anything wrong, other than not being the right person for you, so you should just let them be.