Also, a simpler explanation for the large support for the Democrats would be that SV consists of intelligent, highly educated and well-informed people that wouldn't dream of supporting the extremist, anti-intellectual and downright insane collection of circus freaks the Republican party has become.
Just based on the purely anecdotal evidence of online and personal encounters with SV-dwellers, I would consider most of them to be "open minded conservatives".
The other foundation is the way companies in SV are organized and equity dived compared to traditional companies. This could simply be explained as "pragmatic", which is how most companies view it themselves.
It seems to me the author is trying to project his own ideas on SV.