I have expressed this to my W. I got a deer in the headlights look and a "that makes no sense" response. Mind you, my W is very intelligent and can readily understand this concept. She rejects it because it conflicts with her current desires.
She needs to justify her behavior and must take an emotional view of love. With that view, she is able to become a victim of fate rather than a person making a moral choice. What else can she do, she is not "In Love" and she is powerless to change this reality. She is "In love" with the OM, how can she deny these feelings? How do her friends or family argue with what she feels?
AD - I see your husband making the same justifications. I can understand how a person would willingly deceive themselves. But, in the end, they are lying to themselves. We live in a relativist culture where we tend to view all perspectives as equally valid. They are not. The simple fact that your H believes something doesn’t make it true.
You said:
“Or, at least in the case of my husband, I don't think it's that he has low morals or a looser hold on the commitment of marriage, or is too lazy to work on the marriage. I don't think he's choosing an easy route. I think he really believes love can just go away, and attraction can just be forever gone, even if he didn't believe that before he believes it now because he feels it and is living it.”
He does not have low morals or is lazy. He is just wrong. He feels it and lives it, because it is a self fulfilling prophesy. Once he chooses not to love, or accept your love, it is not surprising that he doesn’t feel love.
You can validate his feelings without accepting the lie. In my mind, this issue is “Black and White”. Unfortunately, everything I read says that this is something your H needs to learn on his own. I wish there was a pill.