It turns out that all media are the proper vehicle for such campaigns, because media that aren't part of them are directly and actively opposing them. Representation in media has huge impact on how people treat other people. When media omit categories of people, those people suffer as a result. Humans do not have the ability to meet enough people to have a reasonably representative sample of the population, and will tend to react with relative hostility to unfamiliar people, or people in categories they haven't been exposed to before. Media representation reduces that bias.
I'm very much not impressed by the intellectual acumen of a 'if you're not with us, you're against us' declaration. That's a statement of zealousness, not reason.
That said, I strongly disagree that the culture war must be waged on every front possible. Some places, like D&D, are far to niche to matter. Whether or not D&D is at the forefront of the war is generally meaningless in the greater struggle. I wish you well (I voted for gay marriage, and support LGBT rights in general), but I'm sorry, I can't get so enthused that I must declare everything to be part of the crusade, and anyone not joyously enthusiastic about participating should be labeled as part of the problem. When you include the vast majority of everyone in 'part of the problem', you should start re-examining your definition of the problem -- you might have gone a bit too far.
What people are asking for is that other groups be treated the same as cisgender straight folks. Adventures have NPCs that are blatently identified as cis (pretty much anyone with a detailed description) and straight (anyone with an opposite-sex partner, spouse, or lover). If you refuse to have non-cis and non-straight people, that is erasure. It is discrimination. It is wrong.
Goodness. I've never seen a D&D module with a Republican in it. Or an Ethopian. I suppose they've been erased in favor of elves and dwarves and whatnot? That's a patently ridiculous claim that a failure of equal time is erasure. Erasure is what happens when you're systematically removed (not ignored) from representative media. You're going too far.
A D&D that includes straight characters but not gay is pushing social issues. It is, in fact, "pushing social issues" more than a D&D that includes mostly straight, but some gay, characters.
This is the point people seem incapable of grasping. Making a character straight is a choice, just as making that character gay would be. If one doesn't need justification, neither does the other. And this includes secondary or indirect references to sexuality, such as characters who are married or have families.
Having an occasional gay (or trans) character isn't pushing an agenda; it's recognizing that people are people.
Sure its not, and I agree with you. I also think that having published 'blank space' for you add more if you'd like isn't a bad idea, and may be even more broadly preferable than trying to keep track of whether or not you've hit the right percentages in game.
I mean, heck, this could easily be a minefield: "The only gay NPC in latest WotC adventure is the bad guy -- what are they trying to imply?!" I understand not wanting to engage in an area where people literally say 'if you're not with us, you're against us.' Which is why that kind of tactic receives so much pushback -- it's not useful because it leaves no room to engage in the middle. Which is where I think your suggestions largely fall, and where mine was intended before I was told that failure to agree entirely was the same as being an enemy.