If you do that, then you have to admit different kinds of imperative code: C-imperative style that can modify any state in the application as side effects, and

If you do that, then you have to admit different kinds of imperative code: C-imperative style that can modify any state in the application as side effects, and Haskell-imperative where you can only modify state explicitly declared as input to the procedure. It's not just mind games, the difference has very real implications to the architecture of the whole program and the control you can exert over unpredictable side errors.