It's wrong to destroy a relationship.
Jeff knows John has been unfaithful to his girlfriend.
Jeff wants John to admit the truth.
Jeff suggests to John he should own up to his actions and ask for forgiveness.
Jeff tells John's girlfriend about the infidelity and tells her she should confront John about it.
John explains and apologizes for his behavior to his girlfriend, and she forgives him.
John is devastated when his girlfriend breaks up with him.