A sword is tempered to make it strong and capable.
If a sword loses it's temper, it is useless in battle.
I've never had a meltdown in public, preferring to do that in private on my own time and terms. It's embarrassing to watch someone lose it, and being yelled at or subjected to raving bouts of profanity rarely inspires sympathy or respect.
Anyone who works every day with people knows that minor and major meltdowns can lurk behind every encounter. I make sure I'm always courteous and pleasant with waiters and sales people and anyone in customer service because I've been on the receiving end of temper tantrums and it ain't pretty to be in that position, especially when whatever it is that's gone wrong is not your fault and out of your control.
Dealing with someone who is angry and frustrated without feeding that anger is sometimes as simple as just backing away, giving them space, and listening to their rant. Then I've learned to ask "What can I do to make this better?"
Lots of times they don't even know what they want. It just feels good to get it all out there. Rarely is it personal. Quite possibly there are many other things going on in their lives that they're having a hard time dealing with, which have little to do with whatever this situation is that has pushed them over the edge.
And seriously, the things that some people go on and on about are so incredibly trivial, it makes me wonder what they'd do if something REALLY bad happened to them.
Calm down. Take a deep breath. Will this matter so much in half an hour? Five days? Two years? In the grand scheme of things it's a hang nail, not cancer. Get a grip.