While browsing these messages, I've noticed a bit of a pattern. The low-desire spouse usually does not change, at least not much, until confronted with a major life-changing decision. One woman recently joined who is expressing great joy at solving her own lack of desire, but only after confronted with divorce. In Michele's book, she quotes another woman who suddenly found her libido, but alas it was after her divorce was finalized.
So I guess it goes like this: "My dearest Jane, I love you and always will. Marriage includes among many things the special bonding that joyful sex brings. But passionate sexual desire is missing from our marriage. Unless we find a way to bring that into our marriage, I think our marriage must end. This isn't meant as threat, but simply to tell you that I am missing something that is core to my own being. I have done my part to try to solve this issue, now it is your turn to work on the solution or simply give up our marriage."
In reality, I think most low-desire spouses would simply issue some insult about low-brow animal needs controlling our intellect, and call the bluff. Maybe the "180" behavior is to quit trying to save the marriage.