Passion as an emotion, I believe, is the intensity for which you feel something. Love or hate or Lust.... it doesn't have a negative or positive connotation to it. One can hate someone or something passionately as well as love. The opposite of love anyway is apathy and I know nobody who is passionately apathetic. Since apathy is to feel nothing for someone/thing one way or another, passion would have to describe extreme intensity of ANY emotion.