So many times we find ourselves challenged by client events. Sometimes, we have to make decisions that are not well received by clients. And sometimes, clients can get angry with those decisions.
It's always important to remember, anger directed at anger always starts a fire that burns out of control quickly.
When confronted with a situation that angers you, STOP, breathe, then respond in a rational, fact based way.
Take the emotion out of the situation. Explain why you made the decision you did, build your case on facts, not conjecture and put water on the "client anger fire" instead of fuel.