Most people care quite a lot about what people think about them. I, however, am different, because I don't really care that much. This means I'm indifferent.
I could do a great big rant about that as a social and psychological phenomenon, but I don't really want to just now. I just wanted to point out that I've found another pair of words that appear as if they should be opposites and are not.
Different = doesn't match
Indifferent = doesn't care