Daniel Cormier -- Jon Jones Told Me to 'Suck His D***'

Daniel Cormier says Jon Jones' good guy image is all BS -- claiming Jon privately called him the "biggest p***y he ever met" and told him to "suck his d***."

It all went down at a UFC media event in Vegas -- with DC saying that Jon is a fraud ... and hasn't learned a damn thing from all of his issues outside of the Octagon.

Jon took exception and they went off on each other ... insane.