I agree that intimidation surrounded some of the commemoration events but these activities were typically separate from the UDC efforts. The UDC‘s mission was averse to generating any controversy that would impugn their controlled narrative, which was contemporaneously referred to as the “Lost Cause of the Confederacy.” Except for their occasional dalliance with rogue speakers who deviated from the script, the UDC promoted a positive agenda focused on memorializing the Confederate soldier without causing offense to the National (Union) interests for North-South reconciliation. However, there would have been no patience for any defense of slavery or the association of it with their purpose.
This is not to suggest that there were not outside forces at work to intimidate Blacks during the monument unveiling ceremonies and other associated events. Confederate reunions were often scheduled by outside groups to coincide with the UDC ceremonies and some undesirable characters were often in their midst.
Brendan Wolfe, a Charlottesville Author, has published a very detailed history on his blog of the fockery afoot at the 1924 unveiling of the Lee monument in Charlottesville. He also covers the post reconstruction tensions you alluded to in your response that still resonated in 1924. His narration of the concurrent evil acts of violence and murder in nearby Danville are extremely disturbing.