"I could care less" is not "I care none at all" nor does it mean "I care very little", and saying it isn't an issue to the meaning of your sentence.
A zealot could care less for their cause. As could somebody who barely cares. And all the shades in between. It is pretty useless to say - you could replace each word in "I could care less" with "blah" and you'd get as much information across.
Agreed! But "blah" is enough, I think, to get the meaning across of "this isn't something I care much about". So it's still an efficient sentence for it's use. This is a sentence that is designed to show disinterest, and it does. How much disinterest is moot, unless you demand of it. Off handed remarks tend to have the leeway of not needing to be defined unless pushed.
" Sir, please sign my petition?"
" I could care less.."
A. " But then you must care some, let me explain why you SHOULD care.."
B. This remark kills dialog and the conversation ends.
If you feel you can press it, then A. if you feel the cause is lost then B.
"I do not care at all for your petition" is a definable shut down of the conservation, where "I could care less" is a means to push said issue if one must.
So, what I am saying is..
Those that use "I could care less" is openly inviting you to make them care more...