dark type has never been about dirty fighting only. umbreon, for example, only evolves by night and is associated with the night and the moon. nothing aobut it is evil or triecky. there are moves like dark void, dark pulse, night break (?) and so on that are not about dirty fighting already.
I'm pretty sure one of Umbreons Dex entries states that its sweat is poisonous.
what does poison have to do with dark? O.o --- Xerneas, the gay-pride Pokemon 3DS FC: 4511-0558-9256