Honestly something like that might have worked back in beta when there was a large community of folks that wanted this content. Of course most of those left before the game even went live though after it was made clear this content wasn't being added for launch. Out of the remaining folks I would guess most left around the time of the Guild Summit like I did.
Seems like only the die-hards and eternal optimists have stayed around this long with the occasional returning player like me. I don't know that we'd even get a big enough turn out for it to make an impression. Sadly BW did a pretty good job of killing off this section of the community.
That said, I'd support anything someone puts together.
I think it would all be about getting the word out. If all we did was talk about it here, I think you're right. But if we contacted LGBT friendly guild officers to ask them to spread the word to their guilds, I think we could see a decent turn out.
A demonstration need not be comprised only of people who are personally invested in seeing this content. I'm sure there are plenty of people who don't have a personal stake in it that would lend their support to the principle.