You can always tell between those who have worked (or have had parents who have worked) in retail, and those who have not. The difference in attitude is immense.
A person will never fully appreciate the full vitriolic nature of the human bean until they have gone through the trial of the part-time position in a general-public-facing position. Public-relations positions in corporate offices don't count, I'm talking real Joe Public consumers, not targeted clients.
The world would truly become a more understanding (if resentful) place, if it became mandatory practice for everyone to spend at least one summer holiday working in a local cinema/restaurant/convenience store/coffee shop/cafe/supermarket/takeaway/video store/take your pick.
I'm serious about this. Wars could be prevented.