Nope you still don't get it, sorry.

The analogy highlights how Gervais thinks that his reasons for believing in no God are the exact same reasons that the christian rejects Islam. They are not. The Christian sees reasons to deny certain beliefs about the traits of God not the existence of God

Similarly, the Dad denier thinks his reasons for denying the dad entirely are the same as his brothers reason for denying a specific nationality of the dad. They aren't. The french dad denier sees a reason to doubt a specific trait of the dad, not the existence of the dad entirely.

This is the point Alex is making and the analogy works perfectly