Sparkly,
No doctor EVER said that ONE TIME can have an effect.
If you are worried about the few minutes less to do Mitzvot, any movie is MUCH MUCH longer than a few minutes and no one is doing Mitzvot while watching a movie. Certainly not any of the contemporary movies.
And watching almost any of contemporary movies is AGAINST the Torah. Does that mean ANYONE who watches a movie is off the derech. You CERTAINLY seem to be saying so.