Two potential explanations: the tech industry can't stop talking about itself on twitter and blogs. How many mechanical engineers do you know that spend a large % of their day procrastinating by surfing the web and participating in meta-talk about the industry. Our day-to-day tool for doing our jobs also just so happens to be a worldwide communication device. Just like the media loves to report on themselves, the tech industry loves to post on the internet about the tech industry, so the effect of a single asshole's comment is magnified by a social network powered shitstorm, further entrenching the meme that tech is full of bigots and causing a flood of discussion and hyper-analysis of it.
The second explanation is that the tech industry is actually less mysogenistic than others, as you have noticed, but ironically due to the lack of widespread mysogeny like you see in areas like finance, when an "incident" occurs, a lively discussion happens because there is a critical mass of non-sexist males, not due to a lack of them. Off course, this feeds into the meme which cements it more as accepted truth, despite any real data or study showing that tech has a above average rate of male mysogeny.
Another possibility is that the tech industry is currently a desirable place to work. People generally don't care if you exclude them from jobs that they wouldn't want anyway, but if other people are having a lot of fun, changing the world, and getting paid for it, it really sucks if you're excluded from that because you lack a Y chromosome. Hence when stories appear about "software eating the world" or Google engineers getting paid $300K/year with $6M retention bonuses or startups getting sold for $19B after 4 years of work, everybody wants a piece of that, and any hint that it may not be a perfect meritocracy is problematic.
The second explanation is that the tech industry is actually less mysogenistic than others, as you have noticed, but ironically due to the lack of widespread mysogeny like you see in areas like finance, when an "incident" occurs, a lively discussion happens because there is a critical mass of non-sexist males, not due to a lack of them. Off course, this feeds into the meme which cements it more as accepted truth, despite any real data or study showing that tech has a above average rate of male mysogeny.