It's actually possible that he wasn't upset to begin with. We had a terrible phone connection, so he may have been interrupting me by mistake simply because he couldn't hear me. Talking fast doesn't mean much by itself, and the list of problems could have been meant to inform me rather than blame me. The trouble we were having hearing each other set the stage for a misunderstanding.
Upset or not, most people don't respond well to being told to calm down. Nine times out of ten, it seems to make an angry person even angrier, and it often triggers anger or defensiveness in someone who wasn't particularly upset at first.
Like me, most people who tell someone to calm down are hoping the person will simply take their advice. But it rarely works that way. The message that is intended is not the message that is received.
- When you tell someone to calm down, you seem condescending. It is as if you place yourself in a superior position, judging their emotions and telling them what to feel and how to act. Nobody likes that.
- The person who is told to calm down is likely to feel that you aren't taking their concerns seriously. The message seems to be that whatever this is, it isn't worth getting upset over, and they are just over-reacting.
- People who are angry usually believe their feelings are justified (and they may be right). Telling them to calm down is like telling them their feelings aren't valid.
Instead of saying "Calm down"...
A better choice for me in the conversation with my relative might have been to say, "I'm having trouble following you. Could you slow down a little?" Slowing the stream of words can have a calming effect. At the very least it will make it easier for you to listen to the other person and give you some time to think about how to respond.
If someone is upset and shouting at you, it is always acceptable to say "Please stop shouting." There is no need to add any speculation about their emotional state or motivation, since that will likely upset them more.
Instead of getting defensive...
When someone tells me to calm down, my preferred response is to smile and say, "I am calm." I say it very calmly.
Another possible response is "That's a great idea!" followed by a request for whatever it is you are trying to get from the other person.
Sometimes it's best just to be straightforward and say, "This is as calm as I can be under the circumstances. So let's just move ahead and try to solve this problem."