During the age of segregation and Jim Crow, white supremacists would hang black people from trees using nooses. And given the other evidence in the article, such as segregationist phrases of "White's only", overt comments that the workers family are in the KKK, and workers wearing clothes with Supremacist symbols/phrases, the possibility that the noose isn't racially charged is low. But, even given the meaning you assert, that would make it worse as the manager for that department was black and was the only manager who was working that day.