"His sexuality, specifically because he’s the ONLY ONE, and because gay men are painted as unathletic in our culture, makes it a big part of the story."
Really? In my experience gay men (and far more prevalent stereotype about lesbians is that they are quite common as female athletes) are regarded as fitness freaks, very competitive, and quite athletic. It isn't that gay men aren't perceived as athletic it's that heterosexual athletes in generally mainstream athletics don't like homosexuals. Basketball, football, baseball, hockey, soccer, even tennis and golf all are generally sports that are hostile to gay men and that is an entirely different problem. Certainly no one who watches figure skating cares one way or the other and probably not in diving either.
Had Matthew Mitcham been a gay basketball player or discus thrower or even a swimmer then it would almost certainly been far too big a story to suppress over ratings concerns.