Competent. Not expert.
Again this isn't a group of friends at a table over beers. This is a community site where people invest time to play. There is a reasonable expectation of competence here.
Let me liken it to NY Taxi drivers. When I hail a cab driver, and get in the car, I enter in to a sort of agreement that the driver knows how to drive. If you've ever been in a NY taxi, that is very, very questionable sometimes. Bad taxi drivers end up giving all taxi drivers a bad image, regardless of how many good drivers are out there, people remember the bad ones. A bad enough experience and people may never take a taxi again.
I do realize taxi drivers are licensed, and DMs are not, but lets not split hairs. My point remains exactly the same. Instead, what do we tend to do...
"Dont blame the driver, blame the whiny passenger for the bumpy, heart-attack filled ride."
"It was the passenger's fault. He shouldve got out of the car when they hit the first detour."