I've clearly never followed the maxim I'm quoting in the post title, but the most cursory trip around the internets confirms its providence.
Some statements I've been subjected to about the gentle craft of roleplaying this week:
 "If you're going to play a system that uses a 20-sided dice you may as well just convert it to [the] d20 [game system] because everything else is just too complicated."
 "D&D 4th Edition removes the beautifully crafted storytelling and deep character-driven roleplaying that D&D is famous for."
 "It's a pretty disappointing campaign unless you have a total party kill (TPK) somewhere in the first three sessions."
 "I don't like D&D 4th Edition because it's too hard for the DM to win."
Hopefully you're laughing with me and not at me, but if anyone's in doubt as to why these are dunce-cappers, drop a comment, and I'll do a post.