I always find it funny when people see someone being aggressive or angry and they decide to say "Relax" or "Calm down". It seems obvious that those things are only going to make the person that is aggressive/angry more so than they already are, yet it's sort of the default response I hear (though I don't really spend a lot of time around angry people myself, so my opinion may not be representative of the general population). I don't think I've seen a single instance in which things don't go downhill once they say it. The person they're saying it to will usually lash out at them, which turns the situation into an unecessary yelling match. History repeats itself, over and over.
Edit: this post is awful;y written, but I'll leave it as is (save for some typo corrections) because it's now past the date of publishing.