Haven Hart, Auburn University Assistant Vice President for Student Development Full Statement:

Auburn supports free expression and civil discourse but does not tolerate harassment, threatening actions or racism. We encourage any student who feels threatened to take advantage of all available resources, including the university Office of AA/EEO (http://auburn.edu/administration/aaeeo/), the university Bias Education and Response Team (AUB.ie/BERT) and the City of Auburn Police Division. 

Also, as you mentioned, the White Student Union is not a university student organization.