What if there are other gays that didn't get fired?
What if the person doing the firing is gay?
According to the decision neither of these would matter. It doesn't matter how groups are treated overall, it matters only if a protected characteristic contributes in any way to the firing of an individual.
And how does a person prove they are gay?
Is just saying it enough?
Yes. I think the Title VII argument could be made even if the firing authority made an incorrect assumption about the protected characteristic.
And if you do provide those details to your colleagues then aren't you violating some harassment statute? Or violating company policies. And that's something you COULD be fired over.
And that is the play I would make as a boss if I needed to fire an alleged gay person. Start the paper trail as usual and then hope that at some point they break out the gay card and go into detail about their sex life and fire them for creating a hostile work environment.
While I don't doubt that there will be people who will flagrantly (or perhaps flamboyantly) abuse this, it seems like there's a pretty slim chance that someone choosing to play the gay card here are going to follow it up with graphic details that would be actionable. A vastly more likely scenario is:
"Jim, you're fired."
"It's because I'm gay, isn't it? You'll be hearing from my attorney."
All that said, the opinion is judicial overreach. Sure, if they passed a new civil rights act they'd almost certainly include LGBTQLAMINASDFOAISNERWELKINC& in the list of protected classes. That said, the law doesn't reference it, and firing someone for a particular kind of sexual behavior is not the same thing as firing them for their biological sex. The opinion gets around this by saying "This man was fired for kissing a man, but if the employee had been a woman kissing a man then they wouldn't have been fired! Checkmate!" This is disingenuous and intentionally removes actions from their context. It might be noted that if a woman kissed that particular man it would likely be considered a possibly criminal unwanted sexual advance given that the man in question is homosexual and therefore might well have resulted in firing.
Whether or not you agree with the outcome it takes a heck of a lot of twisting to get to the point SCOTUS got here.