I've gotta say, I've been flying 121 for two years and not once has anything that you described happened to me. I guess that's what you get when you hire minimally experienced FO's and they upgrade to CA .

Everyone flies fast on the last leg, but I've never had it as bad as you describe. Depending on the buildup and what it's painting in the 20,000 ft level I would've let the dumbass go thru if he/she insisted...just be sure to warn the FA and peeps!