Throw on a business suit (preferably an Armani but any standard suit would work), and then hire two big thugs (both wearing Tuxedos and preferably Italian) to accompany you. Walk up to him slowly and have the two thugs push him into a wall and then duct tape the dudes mouth shut. And then you walk up to him and get as close to his face as possible and tell him using the best mafioso accent you have "I hear you've been saying things about a business partner of Mr. Ferelli, I believe his name is Insert Name Here . We Don't appreciate this kind of slander very well, you rat ******* son of a *****." Then Slap him across the face as hard as you can and then get back into his face again "If I hear you've said a word to anyone about Insert Name Here or our little meeting, your eye is gonna meet this sodering Iron" [Proceed to dangle a hot sodering Iron as close too one of his eyes as possible] Then laugh menacingly, have the two thugs rip off the duct tape from his mouth as quick as possible (be sure to make the duct tape contact the area between his upper lip and nose), and then have one of the thugs sock him in the gut as hard as possible (to double him over) and make a quick getaway.

A. It would scare the living crap out of the guy
B. If you get caught by the police, you'll probably get an award for showmanship