I am thinking that almost all instances of people being awesome occur in situations of plenty, and almost all instances of people being crummy occur in situations of scarcity. Scarcity activates the circuit that says "I gotta get mine before it's all gone". Money, food, status, time; next time someone's getting testy or worse, look for what is scarce. See if you can alleviate it. Also, learn from that instance and see how you can avoid this being scarce in the future.