"YOU ARE A HACK": O'Reilly Gets Into a HEATED EXCHANGE With George Will Over 'Killing Reagan' (VIDEO)

This goes downhill fast. Right at the beginning you can see this is tense. Bill comes out swinging after George Will wrote a scathing column Thursday morning calling the 'Killing Reagan' book a 'no-facts zone' and a 'tissue of unsubstantiated assertions'

GEORGE WILL: "You're book does the work of the American left with its extreme recklessness"

O'REILLY: "You are lying"..."You are a HACK"