PG 13 is a threat or menace if it is allowed to be. It's usually very clear whether or not a movie has "questionable" situations or language by viewing the previews. It's perfectly ok for a parent to say, "No, I don't think this is appropriate for you".
Parents should preview movies their children wish to view and make the final call. One persons PG 13 is another persons R or X rating. (OR G rating for that matter) Movie ratings are meant to be a guide and not a LAW. This should be consistant in all forms of "entertainment".
Kick'em where it really hurts, the pocketbook. Don't spend money at the theater. Select alternative forms of entertainment. Our money talks, the more money we spend, means the more we like something.