I don't understand the problem with "I could care less" - it's an American figure of speech that's all, so it's not "wrong", just different.
*edit - reading up on it, there's a suggestion that it's similar to New York Jewish phrases like "I should be so lucky!" (meaning "I have no hope of being lucky") and "Tell me about it!" (meaning "No need to tell me, I already know about it") both of which have an implied sarcasm and are the opposite to their written or logical meaning.
For me - when someone (usually an American friend or someone in an American film or TV programme) says "I could care less..." it really doesn't bother me as I know exactly what they mean... in fact...