Suggest: 

> NIL values inclusiveness and diversity:  we want to be a space where all people feel safe. By hurting others you will hurt yourself;  membership is a privilege that may be revoked or refused.  Be excellent to each other -- or at the very least, *don't* be *un*excellent.

Rationale: minor edits for passive / active voice.  I also wanted to give context to the idea that our doors aren't always open.  It feels very weird to me, in a backlash sort of way, to say that we want to be "inclusive and diverse" but that we "carefully choose who joins us".  Though I'm reasonably sure I understand the intent behind it, I don't think the phrasing does an elegant (or unambiguous) job of describing that intent, and this is the kind of statement that you **really** don't want to mess up.