Realistically tho the point of language is to communicate, and if an "error" becomes widespread - can you call it an error at all? We all know what the phrase means no matter how "wrong" it may be considered by "learned" people
saying "I could care less" is the same as saying "I couldn't care less", its a double negative, like how saying "ain't no" is the same as just saying "ain't" . . . right?