I'm always slightly intrigued by these questions about discrimination, specifically when it comes to gender.
If myself and an group of mates found that we regularly met to catch up, spend time with each other & get away from not only jobs but also our partners/children & as part of this regular occurrence decided that we would never allow our partners/children to join us, no one care. It would just be a group of guys having male bonding time.
If that group of guys grew and they decided to buy a plot of land to build their own man-cave but kept the same rules of no partners or children would this suddenly become discriminatory? Would it only become discriminatory if they started charging the members of the group a membership fee to pay for the upkeep of the man-cave?
Why should anyone look at this man-cave and be able to demand that women are allowed to join & cause a media stir or take legal action if we refuse?
I also have no issue people setting up private women only clubs too. It does get a bit greyer when when public sports centres allocate time specifically to one sex & not the other, which generally seems to be female only swimming, yoga, aerobics, cross training etc.
Relating back to the Golf Club, if I played golf I probably wouldn't want to be a member of it if it was men only & many would argue that forcing it to become mixed sex would make it a much better place. However I don't think it's right or fair to force one to change against the wishes of it's members as the feel, the atmosphere & the club at it's very core will change.