I think that if the director and/or production wants to make a certain statement through their choice of actors (i.e. a gay-oriented cast for The Boys In The Band etc) that's fine. But I think that race and sexuality can be, and often should be, different conversations. For one thing, race is something that's often visible to an audience (though not entirely so), whereas ones' personal sexuality is generally not (even if we like to try to guess such things).
Plus, what about any number of roles where sexuality is in flux or not even necessarily the point of the character? Would casting a lesbian actress as Anybodys have to be a statement, or is it just casting? Should Brick have to be played by a gay actor? Does casting a gay actor as Bobby provide an answer to the age-old question as to that character's sexuality? Would casting a gay actor as Horton in Seussical mean that the production feels that Horton is gay? Or can't actors just get cast because they're the best choice for the role, regardless of their personal lives?