I don't really care what they say. If they want to take the phrase literally that's their own problem. In my opinion, "could care less" is a better phrase than "couldn't care less" because of the reasons I mentioned before. You use the phrase (however you say it) when you are dismissing something offhand and don't even care enough to give your opinion on it. To be consistent with that sentiment, you should use an indefinite statement which reflects that you haven't even considered the topic at hand.
On the other hand, if you are actually actively debating a topic you could use the "couldn't care less" variety but that would be a poor argument. If you're actively trying to insult someone or refute their points, you've also already proved that you do care at least somewhat about the topic because you've taken the time to actively engage in it.
:arghh::arghh::arghh: