Are there nepotism, favor trading, and walled garden clubs at play here? Yes, of course, this is a field with a lot of money exchanging hands and people are using whatever advantage they can get. Did the tech scene in the bay area attract a higher than average number of gay people? Seems like it, similar to other minorities who are over-represented for various reasons. But focusing on a "Gay mafia" instead of the more universal dynamics that allow money and power to be concentrated in a small population seems like missing the mark and directing public rage at the wrong targets.
We've done it before with targeting Jews, then lately people of Indian and east-Asian heritage, and now we seem to target gay people. If someone thinks the tech industry is not fully meritocratic, then they should tackle the dynamics that encourage that head on - the identity of the people who are over-represented will change over time, but the systemic dynamics that allow a non-meritocratic power concentration will remain.