I kinda hate to trot out this cliche, but the plural of anecdote is not data. No number of posts should convince anyone without additional evidence that they represent a large fraction of women's experiences.
I wonder what sort of proof you are looking for. I too would love to see some studies on this. Is there a percentage at which you would care? In the mean time, I'll send you this link as well -- http://geekfeminism.wikia.com/wiki/Timeline_of_incidents -- to at least show that this exact type of incident happens all the time.
I care now. Bringing up the hypothesis that "the entire community of tech meetups is hostile to women" is a red herring. Whether it's true or not, the response is the same: call out the bad behavior when it happens. The only interesting question to me is the tactical one of how to do it in a way that only embarasses the guilty party, instead of making an awkward situation worse.