So much to say about this issue, but I just want to comment about one small part of what's up, alluded to in other posts too.
Recently we had a fellow in the shop who wanted a men's night because he (genuinely, I believe) felt uncomfortable having women around in the shop - I haven't quite figured out what an appropriate response there would be. Similar to the situation Sasha described - I think the lesson here is that exclusive nights can't just be about creating a space where a certain group can avoid things that make them uncomfortable. That creates a slippery slope where we could end up with a cisgendered only night (because trans folks make some people uncomfortable) or a whites/non-whites only night, or other things we'd never actually consider doing. The point, I think, is that we are in a position where we must recognize the broader context, within our bicycle culture and our cities, that these exclusive/safe nights take place in. The reason we have a women+trans night and not a men's night is that we see that, in Pittsburgh and in our shop, cisgender males typically occupy positions of power. It's that context in combination with an expressed desire for an exclusive space, that makes our women+trans night appropriate.
I agree. The important thing is to combat oppression and give oppressed people a chance to meet and gain power that they otherwise might not have. That is why it is not (for example) sexist to have women only time and it is to have men only time. Women are an oppressed group in this society. Sexism isn't just not liking or even discriminating against a person of the opposite sex, it's the institutionalized oppression of a group. To talk about women who hate men as sexist is confusing and counter productive.
That's my answer to the above--it's not about who is uncomfortable working with a particular group, it's about changing oppressive relationships. In order to get rid of sexism and racism a lot of men and white people are going to have to feel uncomfortable.
Bring it on.
Andy