"And perhaps if others saw more realistic portrayals of poverty in the movies, they might be more receptive to programs that would help them instead of demeaning and punishing them."
I would love an example where 'realistic portrayals' of a given subject in movies led to changes in public policy / public perception.
If anything, I would argue that popular films, just like other art forms, are more likely to serve as a barometer of society's perception/reception of a given subject than as something that ignites the change.
Take the war in Vietnam in the 60's and 70's - I'm not sure you could make 'The Deer Hunter' in '68, or 'The Green Berets' in '78.
Or the war on drugs - movies like Trainspotting, Requiem for a Dream, or Traffic certainly showed a realistic side of drugs and addiction... and yet the war on drugs has only intensified since their popular releases.