'How do I know this and you don't'?'

I am loving a new-to-me website called "Overheard in New York". This one, for example, just cracked me up:

Zero Christians Set to March in Union Square

Guy #1: What, you got a problem with me cursing?

Guy #2: Nah, nah, it's just that, you know, sayin' "holy fuck" is like talkin 'bout Jesus's mom fuckin' his dad and it's not cool to talk about Jesus's mom fuckin' people.

Guy #1: Dumbass, Jesus's mom didn't fuck anyone. She was a fuckin' virgin. How do I know this and you don't? You're the Christian.

Guy #2: What are you talkin' 'bout? How could Jesus have been born if his mom hadn't screwed his dad? Wait, who was Jesus's dad again?

Guy #1: Dude, are you serious?

--F train