To criticize any art for being propaganda is not only a weak argument, but a complete disregard for the realities of art. All art, whether by conscious or unconscious force, serves to reinforce something. Why is it that a particular screenwriter chooses to write a movie about this subject rather than any other subject? Perhaps because a) it is a good story, an important story and b) because it is relevant to their interests and worldview. Why are characters and relationships portrayed in movies in the way they are? Because, unconsciously, the people who make them gravitate towards certain stories that align with their worldview.

Do not make the mistake of thinking that art, movies specifically, are ever apolitical. They are political in what they show, even if they do not mean to be. Hollywood is not an inclusive system, it is run by a select few that choose what is made and what isn't, and as a result, what we see is the ideology of those select few, and occasionally movies that were chosen to appeal to certain trends and audiences.

You can't slam propaganda. As more eloquent men than myself have said, all art is propaganda. I realize that the idea of propaganda is repellent because of the American propaganda of associating propaganda with the "other," vis à vis Nazi Germany, Soviet Russia, et cetera. However, if propaganda is to be defined as the affirmation of a particular ideology, nobody is spared criticism. We have been conditioned to label anything that smacks of propaganda as bad, without thinking for a second about what propaganda really is. Filmic propaganda is the totality of what is represented on screen.

The fact that Hollywood movies did not tackle homosexuality for a long time is not a reflection of social realties, but a reflection of the ideological lean of those in power. Furthermore, even if something exists as unabashed propaganda (Battleship Potemkin, Birth of a Nation) its status as a great piece of art does not cease to be revoked. It cannot even be lessened, since to do so only reflects disapproval towards its message and not the quality of its art.

Sidenote: The idea that "cis propaganda would still be bad" is pretty hilarious. Cis propaganda? Do you mean every mainstream romance movie since the invention of cinema?