I think it should be banned because I don't think Scout needs more mobility options. It's also just as good at finishing off hurt players as Pistol is in my opinion because each shot does more damage and you'll be close when you shoot them with it anyway.
You can also chase Demomen in open areas and jump over stickies they put on the floor to try and deny you and not take damage.
That's just what I think. I'd really like to hear what better and more experienced players think though.