What this comes down to:

Having players you can trust to not be dorks, and having a group in general that's willing to agree when it's time to kick someone that's being a dork out.

As someone who plays and GMs both tabletop and offline games, I notice that people are much more capable of getting away with really dumb stuff when there isn't AT LEAST one of the players willing to call someone out on being a dork. Now, this is psychology at work, because people are more likely to voice their opinions when someone else voices the same opinion. It causes a cascade effect. But if nobody takes the first step and says "Hey, wait a minute," you'll have... yeah, people just running with the guy being tied to the railroad tracks.

Now, I'm not advocating for folks to keep protest signs handy and start a rabble whenever someone does something you even minorly disagree with. Being able to compromise and work together with other players is part of the roleplaying experience. But if someone is blatantly godmoding, or trying to fudge the rules, or otherwise being a general ass, it's probably a good idea to say "Hey, stop that."

...But then again, it sounds like the folks involved in this "secret note from bad guys" fiasco were all very silly people. Your friend has my condolences, [@Tarquin].