It is not safe to assume that he doesn’t already have it. He is making these statements for a tactical purpose of his own. We don’t agree with him, but all we can do is keep repeating the truth.
You’re right - sometimes it’s no use to try to figure this stuff out. I doubt if DT is that dumb that he’ll just play along to keep peace in the family. But it’s out of our hands. He’s not our dad, he’s just a guy we don’t know very well and have no control over.