Good idea or PC culture run amok? Is there such a thing as an offensive Halloween Costume?

The University of Florida has sent a memo to students letting them know it will offer round the clock counseling who may be upset by a costume someone wears for Halloween:

Some Halloween costumes reinforce stereotypes of particular races, genders, cultures, or religions. Regardless of intent, these costumes can perpetuate negative stereotypes, causing harm and offense to groups of people.

...there is a 24/7 counselor in the Counseling and Wellness Center available to speak by phone at 352-392-1575. Lastly, the Bias Education and Response Team at the University of Florida is able to respond to any reported incidents of bias, to educate those that were involved, and to provide support by connecting those that were impacted to the appropriate services and resources."

The school does not outline what constitutes an offensive costume, which makes the matter somewhat tricky. Is Barb from Stranger Things? Is Sexy Ken Bone? What about these questionable ones from Hollywood's elite?