“I don’t care.”
It’s probably the most impolite thing a person can say.
Most of time you hear it without malice or true intent. It’s more of a “I’m tired and want to go to sleep” like expression. It’s a quick and flippant response to something that’s unimportant at the current time. Or maybe it’s a response to something doesn’t that doesn’t garner your attention.
But when you actually mean it, it’s flat out… well… mean.
And sometimes, to get your message across – you have to get mean.