Appeal to Consequence
Arguing that a belief is false because it implies something you'd rather not believe. Also called Argumentum Ad Consequentiam.
That can't be Senator Smith there in the videotape going into her apartment. If it were, he'd be a liar about not knowing her. He's not the kind of man who would lie. He's a member of my congregation.
Smith may or may not be the person in that videotape, but this kind of arguing should not convince us that it's someone else in the videotape
I hope this is of assistance.