I like the idea of a male only forum. It gives them a place to call their own.
I don't see it as discriminatory at all, I am not at all insulted by it. It is good for a man to know he has a place where he can give and get male support. Chat communication is quite different from forum communication.
I post on a site that is for females only and I hang around that site more often than I do on mixed-genders sites.