He is a limited public figure in anything related to this situation.
Probably us calling him an adulterer would be outside that bound.
But, it is the truth, so I don't worry about him suing me.
As a good Presbyterian you know the Old Testament teaching on adultery, and the penalty for it.
Many public figures have done so and won or settled out of court.
Politicians are a different manner but he has not held elective office.