That annoys me, but having said that I think that it does work in the way the film is done as a whole, but giving us an opportunity to see New Persil Gandalf at work, and the wizard who was formerly defeated by Saruuman now able to beat him. But we lose the straight evil of manipulation, and the parallel with Denethor who unlike Theoden is not able to throw it off (admittedly he is being manipulated by someone a lot more powerful).