The word logic gets used in mafia largely to make those who argue for its superiority feel smarter. There are certainly times where logic is incredibly helpful in mafia. But when you deal with as many unknowns as mafia does, the general idea that logic trumps is not valid.
That doesn't mean I think cases are scummy, though. I think players should attempt to lay out why they feel what they do if for no other reason than it in turn gives other players a method of evaluation. It's hard for me to have "gut" on someone if they don't post. Unless I think their not posting is scummy, but that's pretty context sensitive.