Because not every leader in history has been equivalent to Hitler. Vlad Tepes impaled thousands, but most of his victims were invading soldiers. Leonidas came from a slave-holding society (well, all states were slave-holding societies at that point), but died fighting an invading force.
Can a leader not be commemorated if he committed anything that was a sin by 20th/21st century moral standards?
- - - Updated - - -
Then I hope this Cultural Revolution 2.0 stays in the West.