Since I cannot imagine anything but a few cherry picked examples that could have led to your impression, let me use some of my own (the number of cases is low):
The extremely positive reception of Alicorns "Living Luminously" sequence (karma +50 for the main post alone, Anja's great and technical posts (karmas +13, +34, +29) all indicate that good content is not filtered along gender lines, which it should be if there were some pervasive bias.
Even asserting that understanding anyone of the other gender is "like trying to understand an alien" does not imply any sort of male superiority complex. If you object to sexism as just pointing out that there are differences both based on culture and genetics, well you got me there. Quite obviously there are, I assume you don't live in a hermaphrodite community. Why is it bad when/if that comes up? Forbidden knowledge?
If you're interested in one problem that is causing at least one rationalist to bounce off your site (...)
Are you sure that's the rationalist thing to do? Gender imbalance and a few misplaced or easily misinterpreted remarks need not be representative of a community, just as a predominantly male CS program at Caltech and frat jokes need not be representative of College culture.
Gender imbalances and the occasional frat jokes didn't cause you to leave Caltech.
It's possible that user is sensitive to gender issues precisely because it's comparatively difficult and not entirely rationalist to leave a community like Caltech.
It's generally the stance of gender-sensitive humans that no one should have to listen to the occasional frat joke if they don't want to. I agree with everything else in your post; that final "can't you take a frat joke?" strikes me as defensive and unnecessary.
If you've recently joined the Less Wrong community, please leave a comment here and introduce yourself. We'd love to know who you are, what you're doing, what you value, how you came to identify as a rationalist or how you found us. You can skip right to that if you like; the rest of this post consists of a few things you might find helpful. More can be found at the FAQ.
A few notes about the site mechanics
A few notes about the community
If English is not your first language, don't let that make you afraid to post or comment. You can get English help on Discussion- or Main-level posts by sending a PM to one of the following users (use the "send message" link on the upper right of their user page). Either put the text of the post in the PM, or just say that you'd like English help and you'll get a response with an email address.
* Normal_Anomaly
* Randaly
* shokwave
* Barry Cotter
A note for theists: you will find the Less Wrong community to be predominantly atheist, though not completely so, and most of us are genuinely respectful of religious people who keep the usual community norms. It's worth saying that we might think religion is off-topic in some places where you think it's on-topic, so be thoughtful about where and how you start explicitly talking about it; some of us are happy to talk about religion, some of us aren't interested. Bear in mind that many of us really, truly have given full consideration to theistic claims and found them to be false, so starting with the most common arguments is pretty likely just to annoy people. Anyhow, it's absolutely OK to mention that you're religious in your welcome post and to invite a discussion there.
A list of some posts that are pretty awesome
I recommend the major sequences to everybody, but I realize how daunting they look at first. So for purposes of immediate gratification, the following posts are particularly interesting/illuminating/provocative and don't require any previous reading:
More suggestions are welcome! Or just check out the top-rated posts from the history of Less Wrong. Most posts at +50 or more are well worth your time.
Welcome to Less Wrong, and we look forward to hearing from you throughout the site.