Nobody is trying to forget the message. The statues were put up during the Jim Crow era to remind one set of the population who was in charge and who had led the war to keep them forever in bondage -- that was the message. Germany hasn't forgotten the Nazi era, but you won't see statues of Hitler, Goering, or Goebbels in every little town.
The truth is that Lincoln didn't want to have to deal with the leaders of the rebellion -- he would rather they had escaped. John Wilkes Booth relieved him of the problem.