Tabloids ACCUSE actors of being gay but have you ever heard of anyone being accused of being straight? Of course not. Gay bashing, and groups protesting equal rights for gays are still very common in our culture. Just read the paper, watch the news or attend any Republican convention for examples.
One reason that actors remain reticent about being openly gay in Hollywood, even today, is that our society still looks down upon homosexuality. Or maybe gay actors were scared away from the project as playing a gay character would possibly out them. More sense is that two such famous 'straight' actors would help attract more of an audience and distract, even slightly, from it being a 'gay' movie. How careful was this casting made? Are there so few gay actors in Hollywood that none could be found? Unlikely.
Gay love story Brokeback Mountain starred straight actors Jake Gyllenhaal and Heath Ledger.