Problem is, what should be dismissed as derisory makes many Christians panic; they simply do not know how to give the basic arguments for the faith when they're challenged...
And among the basic responses Christians should have for the Dawkins/Hitchens/Harris crowd is what was said by historians much closer to the events -- guys like Tacitus, Josephus, Seutonius, and Pliny the Younger (who had little reason to be friendly to Christianity) as well as the best historical records of all -- the gospels.
Michael Coren has a nifty little article here telling you more.