The reason for the reticence in letting men "in" to feminism is based on experience, from what I've read - it's not uncommon for men involved in feminism to want to come in and take over - they're trained from a young age that it's the right thing to do. So, one of the concerns is having a man come into a movement about women defining thier own identities and place in society, and telling the women that they're doing it wrong. It's a slippery slope because of the various ways in which various bits of patriarchal training can warp good intentions - men are taught to take control, be authorities and to "look after" women. If we fail to keep those tendencies in check, we end up trampling all over a movement that is, at its heart, by and for women. Feminism is, at least in part, about women trying to define thier own role in society - or, to put it in much different language, about dismantling the patiarchy. If men want to throw off thier own patriarchal yokes and define their own role in society as men, feminism isn't ther place to do it.

That there really isn't a good place for men to work at doing so is something that I put a lot of thought into.