This is EXACTLY my point.
Lincolns MANY faults and bad calls are papered over with respect because he did one great thing: he signed the Emancipation Proclamation.
For a long time, it was the same with Columbus. His misdeeds were papered over and ignored because of the one great thing he was credited with: discovering "America".
If you're going to strip away the conventional wallpaper from one historical figure and damn him for his misdeeds, then to be consistent you should treat all historical figures in a similar fashion... including the ones you like.
Columbus was a sumbitch. Lincoln was a sumbitch. They both had feet of clay. Probably neither was really a nice man. But they both did something great, and many people choose to revere them for the one great thing than revile them for the many (presumably lesser) wrongs.