Frank Beckwith has made the observation that when people cannot refute your argument, they often trump it with spirituality. You know the kind of thing I’m talking about. You state your reasons for believing P rather than Q, and your Christian brother responds by saying, “I know that’s not true because God told me Q is true.” Or your Christian sister responds, “You only believe that because you are carnal.” Don’t fall for this cheap tactic.
You could respond by saying to your brother, “Actually, God told me P is true, so I know you didn’t hear from God.” And to your sister you can respond, “Ok, I’m carnal. So can you tell this carnal brother of yours why my argument is wrong, and why I should believe your position/interpretation?”