Insanity in the men's room at the Russell Athletic Bowl on Wednesday -- when a 1-legged West Virginia fan got punched by a Miami fan ... and then screamed, "I used to f**k guys like you in prison!"
While the Mountaineers were taking on the Hurricanes in Orlando ... the two rival fans got into a heated argument at the urinal.
The WVU fan threatened to pee on the UM guy ... the UM guy punched the WVU fan in the face.
A chase ensues -- and that's when the WVU fans drops the prison line.
The worst part ... neither fan washed their hands before leaving the restroom.