Maybe the term we're looking for isn't anti-gun, but contributing to anti-gun sentiment?
No, it's anti-unbalanced-people.
...with guns
...or sharp objects
...or baseball bats
...or a voter registration card
...or any other dangerous thing
It's not anti-gun, or contributing to anti-gun sentiment. It doesn't reinforce a stereotype. The stereotype gun owner is not (around here) either a repressed homosexual bigot, neither is it an unbalanced suburban white woman. The stereotype that movies frequently reinforce is gang bangers, street criminals, villians and super-cops. These are not routine gun owners, and IMHO do no contribute meaningfully to a bad image of gun owners. Nobody confuses Will Smith's "Bad Boys" character with their uncle Harold who has a couple of deer rifles and a revolver.
However I have yet to see any movie that portrays, even remotely accurately, anyone legally carrying a concealed handgun. I think that's because Hollywood writers as a rule don't believe in nor understand the concept of legally carried concealed handguns. Of course, if it's concealed, it's concealed right? How would we know if the characters we are watching in a movie who are not openly handling guns are "gun owners", CCW carriers, or not? Given that maybe 50% of American households own guns, it would stand to reason that 50% of the characters in movies should be presumed gun owners, not just those who are actively using them.
IMHO!
All this talk makes me want to go watch some more movies