Actually, he's Hitler. Nearly everything in the trilogy is an allegory to either WWII or Catholicism, often both. So the way they portrayed Sauron as "wanting to heal Middle Earth" jibes quite well with Tolkien's original intention. After all, Hitler (according to him) was "healing" Europe by purging the non-Aryan races and eliminating all the people with "undesirable" traits or "incurable" health issues.