Should a family be ruined because the husband couldn't keep his hands to himself? What if he comes home with AIDS? He dies, the innocent wife dies, the kids are orphans. What if the secretary files an EEO type complaint? Even if he's innocent of harrassment he still will lose everything. And his family suffers for it. He and his family are far better off if he remembers to only touch what really belongs to him.
Every form of sexual or romantic activity outside of marriage is adultery. A married man should not even give a car ride to a woman he is not married to without a chaperone. Phone sex or masturbation have no place in a marriage. Both fall into the range of adultery.
Note however that the bible gives permission to divorce for adultery. It does not command it. It is the preferred solution for the wronged spouse to forgive.
Again, I think your setting a contradictory standard by saying that divorce should only be allowed in case of adultery and then define adultery as mere phone sex or masturbation. I can just imagine the divorce courts if such a rule were adopted. Wildcat wiretaps, spoogey tissues, where would it end?
It is the preferred solution for the wronged spouse to forgive.
It always is. That's the Christian thing to do.