No, but there's a respect rule that does come up now and then. The core concept is "You can attack teh work, but don't attack the creator" more or less.
Some of us have a thicker skin than others, mind you, but politeness is always appreciated. We're a community of gamers, after all, and we like to be welcoming of people, not dismissive. It's ... hrm. It's like teh XKCD post about today's luck 10,000.

Introducing people to this hobby, teaching them new things, opening new creative windows, be it in mechanical game design, encouraging artists, or just teaching someone who's heard of roleplaying but never seen it before how to throw some dice and get into character. I'll have a love affair with this hobby until I die, and probably for quite a while after that (Seeing as how I've died twice already, long story, look me up at a con sometime and I'll share 'em),
So when someone comes in here with passion, believe me, I get it, I totally do, but rather than go "You're stupid, you don't know what you're doing, I can't believe you'd blah blah blah", if you go in with a plan, laying out where problems are and asking why, rather than tossing insults, you'll get a LOT more responses and a lot more respect. (You in teh general here, obviously, not singling anyone out.)
Everyone makes mistakes; lord knows I do, but the goal is to not repeat them and to always, always, always strive to improve.
Hope this helps!