However - I expect them to know more about the sport they coach than your average fan hanging out on a fan message board.

Can you name any professions that are second guessed as much as sports coaches by people who not only aren't part of the profession themselves but don't even work in the industry?

Sure - sometimes coaches are wrong. And sometimes a random fan comes up with a moment of insight. But by and large - I must trust the coaches to make those decisions over the random fans.