I would imagine any couple planning on marrying (or mating) could go seek genetic counseling to test for any number of genetic diseases. This doctor is doing a great disservice in suggesting otherwise. A good doctor would encourage a man with the knowledge of his fiance's carrier status to have himself tested. Honestly, if I knew then, what I know now about my carrier status and my husbands, I would have adopted children. I only have one that has CF, and I wouldn't trade her for the world, but I would not have chosen to personally take the risk of inflicting this disease on anyone.
Another note, carrier testing that only checks for the most common DF508 mutation could provide your daughter's fiance with false information. While it is the most common, there are nearly 1500 mutations. Neither I nor my husband would have come up on that testing, and yet we still have a daughter with CF. So if he is going to carrier test, it is best to test for ALL the mutations.
Good luck. I hope your daughter and her guy make a good decision and not one they will later regret.