DEAR MISS MANNERS: Could you say something about people who wear backpacks in crowded places, such as elevators, public transit and cafeteria lines? These people don't seem to realize that their appendage makes them cut a wide swath whenever they turn around, and I am forever getting hit by their baggage. I believe the proper thing is for these wearers to put their packs in front of themselves when they are in a crowded area. Mail carriers do it, although they are mainly interested in protecting their letters.
GENTLE READER: Miss Manners trusts that you are not implying that mail carriers ought to be better motivated. Surely protecting the mail is their sacred trust, and it is not their fault that most of it consists of duplicate catalogues.
Backpackers may be perfectly well motivated, and yet go around smashing people. This is why etiquette, unlike the more forgiving social sciences, is interested in action as well as motivation. Goodhearted people who hit others with their backpacks are rude.