Thought Experiment: What if the confederate states had not left the Union because of the slavery question, but instead left over something else not viewed so negatively today, such as import taxes on "widgets". Would it be then okay to celebrate the confederacy?
My own opinion is that it is okay to admire a person, idea, or institution for attribute X even if said person, idea, or institution had attributes Y and Z that are today viewed as deplorable. When judging people from the past you must judge them using a baseline of what was normal at the time.
Six Phases of a Project: (1)Enthusiasm (2)Disillusionment (3)Panic (4)Search for the Guilty (5)Punishment of the Innocent (6)Praise and Honors for the Non-Participants