This might be the reason:
Just as surprising, I have seen a bushy blonde wig on a greasy gay foreigner, who happens to be well equipped to conduct cyberterrorism from a ruined island. It is he who is the villain (though upon his introduction he resembles a hairdresser), flaunting homoerotic impulses in one of the kitschiest performances in the last 182 years. These scenes, these smattering of images, collide and whirl with my sense impressions to constitute the latest Bond film, Brokeback Skyfall.Some people, prominent in the entertainment industry, may be distressed at a flamboyant gay man being cast as villain.
Why do people think Silva was homosexual? I'm thinking very few were actually paying attention to the film. And, even if he was, how does that detract from his effectiveness as a villain? I thought the guy was pretty damned scary. Almost Joker-like (but not quite).