I have good reasons to believe that there are simply less nerdy women than nerdy men

I'd be interested to hear them. I'm aware of the stereotype but not any evidence (other than perhaps dubious IQ data).

Other than that, your comment matches my impressions. I have in the past seen nerdy friends of mine go to bars "to meet women", and had to ask, "Why would you do that? You'll just meet women who like going to bars!"

Also, I've found that most people seem stupid, so I imagine if I were the sort of person who specifically aimed to meet lots of women, I'd likewise form the impression that most women are stupid. It seems like an easy mistake of generalization for someone with nerdy male friends and average female acquaintances to think "women are stupid"; there but for the grace of FSM go I.