What I find a bit remarkable is how they lost control of their club dynamics so severely. I've been a regular attendee of a few hacker spaces that were open to the public but never had the problem they describe.

I think maybe a key aspect is ensuring that all men, particular the ones that are classically unattractive (even repulsive) feel welcome as valued equals. Many women cannot countenance this and will try to shape group membership to be more agreeable; those women are free to leave. The rest are welcome to stay and at that point there shouldn't be any issues.

(Of course it goes without saying that actual harassment isn't tolerated, but being a smelly fat slob with a heart of gold doesn't count.)