When I first saw this, it was from flipping through the channels and I came in at the violent conclusion when Travis Bickle (De Niro) finally snaps.  I remember being surprised by the graphic violence, it being an  older film.  The story is a little dim and definitely unpleasant at times  but so is life.  I believe that the idea of a man becoming sick of crime  and filthy surroundings and has his boiling point makes sense.  See it for  yourself and try not to judge it based on bad reviews, especially Leonard  Maltin's.  De Niro was great in the film.  *Scorcese plays the nutty guy  spying on his wife.