When someone is explaining something to you, usually their motivation or reasoning for doing something, if it doesn't make sense, if it's not logical, it means they're telling you a story, they're not telling you the truth, there is another agenda, another issue they're keeping from you. To try to discuss with them why what they're saying doesn't make sense is pointless. They know it doesn't make sense. They know it's a lie. Better, perhaps, to confront them, gently, with the fact that what they are saying doesn't make sense and you would prefer for them to tell you the truth, however inconvenient that might be.