I 'Aint Afraid of no Ghosts

In the highest corner above many urinals and toilets across campus, there is written "I AINT AFRAID OF NO GHOSTS" in all capital letters. These are the sanitary venues in which the phrase has been seen so far:

Spencer Art Building, 3rd floor, urinal in mens' bathroom
Sage F, 2nd floor, above toilet
Greylock Dining Hall, 1st floor, above the urinal in the mens' bathroom with "IS THIS ALL" and "yes"
Bronfman Science Building, 2nd floor, urinal in mens' bathroom.
Clark Hall, urinals in mens' bathroom
Bronfman 3rd Floor, Psych Urinal