(The people producing those videos say he's "producer and co-writer". Cynical-me suspects that "Gamergate fans" think he must be the real driving force because Anita Sarkeesian is a girl and therefore not to be taken seriously. I do hope cynical-me is wrong. Not-so-cynical me thinks Sarkeesian is more likely to be the real driving force because, other things being equal, a woman is more likely to feel strongly about this stuff than a man.)

Since it's been brought up...

As far as I can tell the best evidence they have for this is a widely circulated video (from before FemFreq) in which she says she's "not a fan of videogames".

And Mcintosh clearly "feels strongly about this", as much as any woman I've seen. The Gamergate people created a whole hashtag to display his tweets (#FullMcintosh), which also became, incidentally, what they use to indicate that they think someone has gone particularly far down the SJ rabbit hole.

Personally, I think the conclusion Viliam mentions doesn't rest in very solid evidence, but it's not far-fetched either. (meanwhile, the "because she's a girl" hypothesis looks very unlikely to me)

What, by the way, makes you think that Anita Sarkeesian doesn't truly believe in her cause? I've only seen a small quantity of her stuff, but what I've seen looks sincere (and fairly plausible) to me.

I'm not sure how familiar you are with videogames, or which of her videos you've seen. But I can't imagine how some of the ones I've seen could possibly have been made without outright dishonesty.