You're not thinking about the meaning behind the words. As I said, it's false. There was a time when you cared less than you do today and therefore to say that you couldn't care less is false. You could and did care less at one time in your life.
To say the phrase in a logically correct way you would have to qualify it by saying something like -- "I couldn't care less, unless I didn't care at all"
Again, just because you know something to exist, does not mean you care in the slightest about it.