I don't want to be there for a self-destructive friend
Why wouldn't you want to be there for them?
I just don't want to take care of him.
It's reasonable to not want to be apart of someone elses self-destructive behavior. If you feel like you are contributing to the degradation of a person then it's in your right to stop and step back out of the situation.
I think I will consider your advice.
I'm glad you will! Sometimes we need to be there for friends whether we feel like it or not.