Floyd Mayweather -- Stop Questioning Bieber Friendship ... 'It's Racial Profiling'

Floyd Mayweather says people who are shocked by his friendship with Justin Bieber are simply "racial profiling" ... and need to stop making assumptions about him because he's black.

Mayweather was in Chicago promoting his upcoming rematch with Marcos Maidana when a reporter dared to ask if Bieber and Johnny Manziel were really his friends ... or marketing partners.

Money artfully negotiated the Manziel question ... but when asked what about his "odd" bromance with the Biebs, Mayweather threw the race card like a it was a left hook.