When there were only a few "geeky girls" around, they were a novelty, and there weren't enough of them to affect change in the workplace. I remember those days. We had lots of highly sexist/racist terms people would just throw around without thinking. Look up "BCH, RCH, and GCH" and the mnemonic for remembering resistor color that begins "Black boys" for example (I won't repeat them). Cheesecake calendars and centerfolds were also displayed prominently at desks. And the women there had to tolerate it. They had no choice if they wanted to stay.
But starting in the early 90's, women starting getting enough power to force companies to enact sexual harassment policies. The calendars disappeared and some topics of conversation became forbidden at work. And many men resented this.
So the trolls learned from this, and thus any woman who starts to be listened to in other male-dominated areas must be destroyed as soon as possible. This is what Kathy Sierra said in her posting. Because, by default, they are not deserving of the attention.
It's the same dynamic that has kept Rush Limbaugh on the radio for 30 years.