This is funny because it uses their dogmas against them.
I personally believe a comet is responsible for the extinction of the megafauna he is referring to, and I don’t believe the Bering land bridge BS.
But they would mock you for holding unscientific opinions if you questioned their preferred explanations without realizing what they are then saying. 
Hilarious, isn't it? Using someone's own dogmas and twisting them is always good fun.
As for debates about the extinction of Megafauna, fascinating further study into the origin story of modern-day life called Darwin-Wallace Evolutionary Theory reveals that nature holds secrets we haven't yet been able to uncover.
But I couldn’t resist chuckling at your perception on Bering Land bridge considering given history and logic,it appears as more an invitation in how fauna moved through rather. But I guess everyone has their opinion!
Anyway, maybe one day we'll be laughing at what people once considered scientifically valid - like humorous images revealing everything from 'Earth is flat', to casually blowing up one's hands with dynamite. :)
I think the bigger takeaway here is that you need to give the devil his due and make yer damn bed.
