Even that's weak sauce, what they would want to say would be more like "I can't believe I could care even less than I already do, but you've proven me wrong".
A better usage is when you someone doesn't expect you to be that interested in something, and you say, "Hmmmm, I could care less about this" which means you're actually somewhat (and surprisingly) interested and trying to state that in a sorta clever way.
Example of proper use of "I could care less":
Leftie: "If you care about Democracy, you'll give Biden a chance!"
Me: "I could care less, and you're helping me get there."
Even that's weak sauce, what they would want to say would be more like "I can't believe I could care even less than I already do, but you've proven me wrong".
A better usage is when you someone doesn't expect you to be that interested in something, and you say, "Hmmmm, I could care less about this" which means you're actually somewhat (and surprisingly) interested and trying to state that in a sorta clever way.
Well excuse me!
Lol :P