I just heard the audio. When the guy says that to Fredo, I just bust a gut laughing. It was so obviously said with tongue in cheek irony after Fredo had erupted in anger.
It was just perfect at the right time. It was the perfect comeback you normally wish you gave when you think about it the next day. Kudos to the guy for being so quick.
LOL, I know, very quick on his feet. In effect rubbing Fredo's nose in it, and then allowing Fredo to demonstrate why he is called Fredo. It culd not have been choreographed worse for Fredo, and it was completely spontaneous.