I dont recognize a double standard. I think if your looking for a double standard or an anti gay campaign your gonna find it. I work at an adult bookstore. We have tons of lesbian porn, gay porn, and bisexual porn, yeah I said it, Bisexual porn, just because Larry Flynt or John Stag dont promote man on man does not mean the whole industry is against it.
They gear their material towards a target audience, as do Falcon and other gay media companies.
I think either a) your looking for the prejudice which means you'll find it, or b) your looking at the wrong porn to find something that satisfies.