A wife being unfaithful to her husband is not something to be happy about because it means that the trust and commitment that were once there are now gone.
Consider the statement "I just found out my wife of 10 years has been unfaithful to me.". Based on this "I am absolutely thrilled that my wife of 10 years has been unfaithful to me" a true statement? Yes, no, or I don't know?