In one of the dumbest marketing moves of ALL TIME, the Cleveland Cavaliers ran an in-arena video during Wednesday night's game ... showing a male Cavs fan SLAMMING his GF because she's a Bulls fan.
It gets worse ... the man justifies the beating by saying, "Bulls fan? I didn't know you were a Bulls fan!"
At the end of the video, the woman resurfaces with an ice pack on her head ... and wearing a Cleveland shirt.
No word why anyone in the organization would green light this ... but you can only assume someone's gonna get fired.
By the way, the woman in the video describes herself as a production assistant for the Cavs.