Robert E. Lee was a popular figure everywhere in the country, not just in the confederate states. It is sourced from a mixture of white supremacy, backlash against Northern occupation of Southern States, the destruction of their slave-dependent economy, the destruction and bombing of Cities like Charleston, Richmond, and Atlanta with the result leaving the cities in ashes.
The biggest cause of the reaction to this statues being removed or any attempt to change the South, is centered on race and someone else taking away the good old days, a fictional depiction you can see in one of this country's most "treasured" film classics "Gone with the Wind."
