There was a long thread about this type of editing on the AC forum a few years ago, which was really interesting. A few posts talked about the companies responsible for "editing" movies for airplanes, and the huge amount of money they make - and how expensive entertainment licenses are for airlines.
I can't speak to UA specifically, but different airlines - and even airlines with flights to certain destinations within a single airline - have stringent requirements. From swearing, innuendo, nudity, etc., some airlines even require all editing out of anything sexual, any sign of drinking, or even of smoking (Turkey does not allow you to see any smoking on TV, even).
Airlines generally have a list of restrictions they send to the editing company, that covers the majority of their requirements. As others have mentioned, for some movies it, well, destroys most of the intent of it.