I don't think that "homosexuals exist, and are people just trying to live their lives like everyone else" is a political cause or point of view so much as it is a basic fact.
Absolutely. I agree with you 100%.
However, a significant percentage of the population nor the ideology of the source material does not share our (factual, scientifically supported) beliefs. All I'm saying is that there is a time and a place for advancement of one's ideological and that a D&D adventure probably isn't it. It's been tried. Take a look at Blue Rose - but for me is falls flat and looks more like out of place political pandering than a real attempt at building a believable world.
As an American who worlds in the developing world promoting democratic values and tolerance, flaunting of one's ideologies in parades, marches, and media does little more than fan the flames. Every time, there's a well publicized LGBT march somewhere in the world, my job becomes exponentially more difficult, as intolerant bigots use it as an example of the abnormal behavior displayed by the prominent members of that community.
I already have students who make fun of the half elf bard being a transvestite and the the fiend pact warlock shows us that all Americans support devil worship. The American media has no idea what type of image they are creating for us internationally and how difficult that image is to correct. Political statements need to carefully thought out, no longer only in terms of an American audience, but an international one, too.
You're asking people to provide evidence of a case where something from medieval times didn't cause any political drama, but was somehow noteworthy enough for the facts of it to have been passed down to us in tact from medieval times.
You'd be surprised by the things I've found in the Tower of London. While working on my master's thesis, I even found prop lists scribbled on old bits of parchment for Shakespeare's plays at the Globe. Because people were in the habit of writing letters back then, many of which are addressed to lovers and mistresses, I would be surprised if you couldn't find something to prove your point in one archive or another, should if have existed. If it wasn't a big deal and wasn't causing any drama, the letters wouldn't have been purposely destroyed, would they?