He thinks that I only dislike this relationship because society tells me that it's wrong. Admittedly, that's part of the reason I dislike it.
First of all, he is trying to play you and make you think you are wrong to be against this R. However, are you saying that you would be okay with it if society was ok? I doubt you would be, but if you would be then why do you care what other people think? It is your life and your M.
I would not tell your H that you will be here waiting for him because it doesn't give him any reason to end it. He has both of you, there is no need to make a choice.
Personally, I would tell him that you love him but you will not participate in a M that includes a 3rd person and then I would go about building my own life, being friendly to him but not open to playing husband and wife. The vets may have different advice...
M 46 H 44 D 12 S 8 M 9 T 11 BD 2/15/13 "Makes sense to stay together" 5/12/13 Agree we are 'healing' 7/13 Definitely Piecing 9/13