A year on, and we have new reflection on the impact of the US Supreme Court's ruling on same-sex marriage. You can read it at First Things.
The author has some very astute observations. Principle among them being that secular society is aggressive in promoting same-sex marriage as neo-orthodoxy for the civil society.
This said, I admit to being somewhat bewildered by the author's insistence in describing the more extreme progressive ideology that has dominated cultural opinion, law, and popular ethics as "new gnosticism."
The Gnostic material we have suggests a religious worldview that was invested in extreme asceticism, sexuality being filtered through ascetic ideas. One exception might be the Sethian groups, although this is such a murky area of scholarship that we have to be careful about identifying homosexuality among the sect.
There are theories that Sethian Gnosticism has some connection with the worship of the Egyptian deity Set and that the latent homosexuality in much of Set's mythology was assimilated into a Gnostic Christian framework. The theory is tenuous and is largely supported by suggestion. Linguistically, the pronunciation of Seth and Set are identical in the ancient languages and the Gospel of the Egyptians (also known as the Book of the Great and Invisible Spirit) is the most thorough Gnostic text that follows a principle of inversion. By inversion, we mean that the text routinely, if not systematically, takes everything canonical scripture/religion identifies as holy and posits it as demonic, and everything that is demonic as the true source of salvation. This includes a reference to the "holy cities of Sodom and Gomorrah" that were destroyed by a false god. Given that the account of Sodom's destruction positions homosexuality as the sin that drove God to destroy the city, it is believed that this portion of the Gospel of the Egyptians (a prime source of Sethian Gnosticism) intimates that, following the principle of inversion, homosexuality was practiced or at least seen as a source of gnosis, in opposition to the dominant strands of Christianity which condemned it.
Does this equate to a new Gnosticism sweeping the West? I'd be very careful about stating that. Yes, a new civil orthodoxy is positioning itself and it forcefully marginalizes anyone who disagrees with its articles of faith with utmost efficiency by means of media. But, let's be honest, there isn't a single metaphysical, spiritual, or supernatural element behind this new orthodoxy. It is, plainly, an unbridled materialism with which most forms of Gnosticism would have disavowed as barbaric.