I've attended several gender balance events (in politics, more than tech) and been one of the 2-3% of the audience who were male. They were some of the best I've been to, and I wish more dudes would turn up and learn from them.
Even if I disagree with the majority opinion, it's better to turn up and ask one polite awkward question than to just leave it to people who wouldn't question their own ideas there (making it a less interesting session).
How is an invitation for guests to bring their partners make an event a private club?