LAS VEGAS – A left straight – and a few more left hands for good measure – ended the argument over whether  Conor McGregor (16-2 MMA, 4-0 UFC) was worthy of fighting  Dustin Poirier (16-4 MMA, 8-3 UFC). The Irish featherweight earned his fourth straight UFC win, putting his most significant opponent in Poirier with a flurry of punches in the first round. The featherweight bout was part of the main card of today’s UFC 178 event at MGM Grand Garden Arena in Las Vegas