First and foremost the best actor who audiences should get the role period IMO. But I also support an LGBT actor getting an LGBT role for one reason a lot of straight people including actors just aren't comfortable with performing acts of gay intimacy I'm not talking about sex but intimacy things like hugging, holding hands, or kissing and it comes off as inauthentic and clunky. I'm straight and you can always tell when an straight actors heart isn't in it and their body language with their love interest comes off like friends or they're kissing their aunt or something.
Before someone says well then gays shouldn't get straight roles by that logic. Well some shouldn't if it comes off as fake but many gays spend a portion of their lives in the closet and thus try to pass as straight and have relationships with people of the opposite sex and become comfortable with acts of intimacy with the opposite sex even if they don't get much or any enjoyment on a sexual level from it. This comfort zone is why I feel gay playing straight works more better than straight playing gay.
But then again why worry to quote RDJ in Tropic Thunder "Man everyone's gay once in a while it's Hollywood."