Really? Do you fire me if I say 'my wife really likes that show, but I haven't gotten in to it"?
If someone wants to keep their sexual orientation private, that is absolutely their right, but people do talk about their lives. If you say "don't talk about sexual orientation" you're effectively saying "straight people get to be out, but gay folks stay in the closet."
I hope and kinda suspect that what you really mean is that if someone doesn't say something that indicates their orientation, it's no one else's business. That's certainly a necessary attitude.
But you also need to understand that most straight people are "out" by default, without ever thinking about it. And it needs to be understand that gay and lesbian employees are equally free to be open about their significant others (not sex itself--that's a different topic).