A guess as to why there is tech sexism
Guys who aren't born with stunning good looks or natural athleticism or incredible people skills need an alternative route to becoming "attractive"- usually something in the vague making money / being successful category. They believe, with good reason, that becoming successful will make them more attractive.
But, similar to the case in the olympic village, the same dynamic doesn't exist to the same degree for women. I'm sure most of us guys (I am a guy) DO think its attractive when members of the opposite sex are successful (or at least say we do), but I think there is still a big group of guys who have the olympic village mentality. So how does this dynamic translate into sexism?
If you (as a man) think your ability to find a good partner depends on your job success, and you see a women trying to compete, you probably have many semi-conscious thoughts like "you don't really need this, but I do- you aren't serious the way I am". That line of reasoning is utter bullshit, but if you adopt the axioms of the olympic village male, its a pretty rational response. If you truly believe that success is more important to you than a woman, you are going to be sexist in the workplace, guaranteed.
If this hypothesized dynamic (i.e. the belief that upward attractiveness mobility is possible for men but not women) is real, then it's increased by the fact that tech-people, via self selection or otherwise, tend to be skewed (albeit slightly!) toward needing success/money to be attractive, as opposed to looks or athleticism or charm etc.
I don't know if this is right, or even close. It seems to kind of make sense to me though. What do you think?