The situation you posit is a valid hypothetical, and one that is more common than a lot of people care to admit. There are a lot of married women who (even after years of couple's counseling, therapy, etc.) simply DO NOT EVER want to make love again, and the husband is STUCK with the choice of divorce, cheating, or just sucking it up and spanking it till he dies.
Divorce is probably the most honest and open option, but many times finances or children make this impractical.
You're fighting an uphill battle here -- everyone is either extremely judgmental and rigid or else is of the "Just get a divorce" mentality.