Even though this clip is on YouTube, it is taken from radio show and is thus audio only. Even so, John Warwick Montgomery effectively demonstrates just how speculative, and even silly, Bart Ehrman can be.
The radio host, who had interviewed Ehrman on a previous occasion, played clips of Ehrman and then let Warwick respond. It reminds me of the proverb “The first to plead his case seems right, until another comes and examines him” (Proverbs 18:17 NASB). The only difference being that if you listen carefully to Ehrman first, he’s not that convincing to start with.
Related to this, see my Open Letter to Bart Ehrman.