How to choose friends and enemies in regards to practice

I'm not really sure who I should cut out of my life and who I should keep ties to. I like to give most people the benefit of the doubt, even I know they have some hidden malice against me I ignore until it seems like it needs to be addressed, but I keep finding that I need to cut these people out of my life eventually. And you know,.. I have chosen to protect friends from others,.. and as time passes I find out my "friends" were actually very vile people and I have to apologize for defending them. I really don't like playing this friends and enemies game because I so often lose, I can't call you all friends or all enemies and I can't be neutral when I know one is harming others. I'm ready to cut anyone out of my life, but I can find fault with virtually anyone and I'm already very selective about who I keep ties to.

I don't want the negative influence of failed or insincere practitioners, or ones that are just having their mental problems and want to drag me into it. I've thought about you know, being the bodhisattva just bearing with other's difficulties unbiased, but I think my own energy is faltering due to this and it's best I isolate myself from all but the best practitioners until my energy and direction are restored.

So,.. how do I pick people to keep in touch with and to abandon to god knows what the world has in store for them?