So this is something I can support:
On Monday, Chief Judge Robert Katzmann of the 2nd Circuit U.S. Court of Appeals wrote that anti-gay employment discrimination is almost certainly prohibited under existing federal law. Katzmann urged the 2nd Circuit to reconsider precedent holding that employees cannot sue for sexual orientation discrimination under Title VII of the Civil Rights Act of 1964, citing recent legal developments that support an expansive interpretation of “sex discrimination.”
This seems to be a relatively simple matter. Did the drafters of Title VII think they were prohibiting sexual orientation discrimination when they barred employment discrimination “because of sex”? Likely not (although there is usually a surprise or two when the historical record is closely examined). But the article notes that SCOTUS recently held (in the words of the article) "sex discrimination encompasses “sex stereotyping”—mistreating employees because they do not conform to gender norms."
From that decision it seems the only logical conclusion that "sex stereotyping" can only include discrimination on the basis of sexual orientation, as not conforming to "traditional" gender norms. Indeed, even without the sex stereotyping decision, and as the judge notes in the cited decision, discriminating on the basis of sexual orientation "treats otherwise similarly‐situated people differently solely because of their sex." And is for that simple reason sex discrimination.
In my mind that is enough, full stop, and this is clearly covered by Title VII. Of course, the 11th Circuit thinks differently because... it does. No really, the 11th Circuit cited a previous case that said simply "discharge for homosexuality is not prohibited by Title VII." Full stop. Not even "because reasons". Just because. Truly those judges have dizzying intellects.
Ultimately, I have to guess that this will be taken up by SCOTUS, where I would guess there are at least 5 votes for the view that Title VII covers sexual orientation discrimination. As Justice Scalia said about Title VII when an employer that it didn't cover male-on-male sexual harassment: "Statutory prohibitions often go beyond the principal evil to cover reasonably comparable evils, and it is ultimately the provisions of our laws rather than the principal concerns of our legislators by which we are governed."
Update: I meant to add that, ISTM, this is a perfectly fine, logical, and respectful of the "rule of law" way for the common law to expand a statute beyond the "intention" of Congress (or the intention of the mythical gigantic prescient perfect demigods of yore we sometimes refer to as "the Framers"). Indeed, I don't know how else this is supposed to work - applying a vague and general statute to specific and sometimes unanticipated situations. I would guess that if you asked the drafters of Title VII what they meant by "discrimination because of sex" they would say something like - you can't fire or discriminate against a woman because she is a woman. But that only gets you so far as you need to ask what does discriminate against means and then what does "because she is a woman" mean. This question is answered above - treating otherwise similarly-situated people differently solely because of sex. Very simple, and yet leads you to places where the drafters would not have gone - and indeed may have explicitly said they were not going had you asked them (and in fact they may have said this).
But, we have a common law system, and this ISTM is the way it's supposed to work. Lazy (or even non-lazy) labeling of this approach as "activist judges" will not suffice.