I find that some people are just not suited to this sort of situation. The problems start when people take things personally and then start flouncing off saying "I'm not paid to put up with this" Actually that is exactly what you are paid for and you have to learn to rise above it and keep a smile on your face. It's just that sometimes you'd like a bit of support from management (some companies are much better than others, I've mentioned my feelings about Sainsbury's before) If you are being pressured from above to meet unattainable targets it makes it more difficult to cope with everything else.
Wicked Little Letters? (funny film of a long-forgotten case)