Are they being assholes simply because they're nervous about your team and whether you're going to deliver, vs. make them look like, well, assholes? Maybe they're insecure and frustrated about that, and about their own inability to evaluate your work on a technical level. Sounds like a little "explanation for a non-technical audience" and some reassurance and empathy are in order. Sometimes assholes are assholes because they're scared, and they think being an asshole is the only way to handle it. Although a firm but polite reminder that you're not going to eat their shit is probably a good idea too. You've set a bad precedent by allowing it at all. Be the mom AND the dad to these little kids.