Many scholars argue that controversial monuments promote a false version of history through valorizing leaders who committed treason, promoted violent colonialism, or supported racism. These statues portray these figures as heroic but they were actually on the wrong side. If this is the case, we would best promote honest narratives of America's history by removing controversial statues.
Also, it might be irrational to claim that removing statues will erase our memory of history. We have many other institutions, like museums and schools, that teach us about the past. With these in place, it is unlikely that the American public will develop widespread amnesia of the past anytime soon.