I think who is treated with respect by whom has actually a great deal to do with what people are used to, what has happened, and was it originally that way? If everyone started out gay, and there were the few straight odd ones out, I think a lot of people ( as there are here ) would not treat them respectfully, though it may be gained after time.
Personally, I think some people that say straights would be treated with great respect are basing it on the fact that they know what it is like to NOT be treated that way. If they didn't know what it was like .. who's to say?
Regardless, referring to brokeback mountain .. I am not gay, but I do have friends that are - and if someone isn't comfortable with watching that movie -- don't. Rise to the Challenge