I guess the writers could resist throwing an anti-Christian viewpoint in it. There were a number of different religions of all kinds that sprung up in the Roman empire of that time. I would sooner believe it was his own arrogance considering what he just said about the limits of his own memory. The part about Columbus and believing the Earth was flat bugs me a bit also.
I might have to watch it and see.
In general, if someone could be killed, the amazing part would be the the person had survived that long and hadn't been caught up in some disaster or war or famine. Or just be killed by someone since he was always a stranger wherever he went.