I think it is just a matter of time.
Hitler did not become well known for being kind and gentle. But Attila was a really bad guy, too. But after hundreds of years, we no longer associate fear and killing with him too much to make him unsympathic.
Perhaps will Hitler be the German leaderhead in 400 years? Right now it is too early to see his unhuman politics without emotion.
George Bush might become the American leader, the one who conquered Mars and Iraq - time washes away most negative aspects and he will probably be remembered of that, who knows???
BTW: Each Civ should have a female and a male leaderhead to chose from. Or perhaps even more, e.g. Charlemagne, Napoleon, Joan, Lous XIV... - the French had lots of great leaders.
I would not mind to have a German Hitler-leaderhead, but think of all the trolls that would abuse this, usually the same who mask themselves as Darth Vader or Darth Maul... cool dudes with little respect or brain.