I can't speak for Silicon Valley, but I have one verified datum wherein I interviewed for a position and received an offer. I wanted to negotiate on the offer because I objected to the expectation for a 45-hour work week at the same pay as that prevailing for similar jobs with 40-hour weeks. There was no negotiation. I literally did nothing more than question the 45-hour week. They didn't even withdraw the offer; they just cut off all contact. No call was answered or returned. No e-mail received a reply.

During the interview, they had mentioned that they were having trouble expanding at their headquarters due to lack of available qualified employees. Gee. I wonder why.

Weekly hour expectations for salaried exempt workers is already a suspect practice, in my view, but expecting work outside of normal business hours is definitely selecting against candidates who are not unmarried and childless. Schools, preschools, and day care businesses operate based on normal business hours. Generally, if your spouse works, you want to come and go at the same times of day. You don't want to live the rest of your life in cubicle farms.

Maybe the tech industry is not racist. Maybe there is just one particular demographic that just cares less about exploitative work arrangements. Maybe that demographic has historically had less reason to distrust authority. Maybe the quality selected for is not age, race, or sex, but sheer naivete.