What you describe sounds to be like the rhetorical strategy called apophasis (ə-pŏf′ə-sĭs)--alternately, praeteritio or occupatio, which Harris defines as a rhetorical device which
"asserts or emphasizes something by pointedly seeming to pass over, ignore, or deny it. This device has both legitimate and illegitimate uses. Legitimately, a writer [or speaker] uses it to call attention to sensitive or inflammatory facts or statements while he remains apparently detached from them."
For one thing, if a person truly forgives another person, he or she will refuse to bring up the hurt again in conversation, either with the person who did the hurting or with others who were not initially aware of the hurt and the circumstances surrounding it.
The person of whom you speak, however, is demonstrating he has not truly forgiven the person who hurt him, and he does so by simply revivifying the past hurt. Evidently, to him, the hurt is not "water under the bridge" and neither forgiven nor forgotten.
For this reason, his use of apophasis is illegitimate in that it is an attempt to sour other people's opinion of the person who hurt him and whom he supposedly forgave.