@Riley1969,
To me, your reaction was very much about the level of your daily communication and level of emotional intimacy you have with you wife. Although you don't say (do you?) how much your wife informs you of her every thought, feeling, and experience, it seems to me this "proposal" came so far out of the blue nowhere that it raised a red flag in you. In other words, it seems as if she is not such a "communicator" that she tells you of her sexual and related feelings or of her history, etc. and that this was not an ordinary communication--one that you were used to. I kept most of my sexual life private from my husband and didn't share much with him and then handled all such things in my own way--I almost always told him very little in order to keep the domestic embers warm enough. If I had told him something like this, he'd have been plenty angry. Do you see what I mean? Like me, your could have kept you out of it and kept it a secret and handled it totally differently-- laughed at and ignored it. Why did she even tell you of this proposal?