There is an old joke about railroad worker that gets stuck cooking because he complained about the food. Realizing he hated the job he set out to get someone else to complain about the cooking. So he made a pie out of moose turds. A giant of a miner came in and sat down and took a big bite! Can you guess what happened?
When my kids were young I coached T-Ball and Coach Pitch Baseball. Those with this experience will tell you the kids are seldom a problem. One day during a critical game one of the parents, a consistent magpie and critic, was in rare form. He criticized the coaches and the kids as he sat on the sidelines. Growing frustrated, I decided I had reached my limit. I walked to the third base coach and told him he looked ill and should sit out. He assured me he was fine and I assured him he was not. He got the message and sat down. I went straight to the critic and told him to coach third base. I did not wait for a response as I turned and walked away. As I got to the pitchers mound I turned and saw him approaching his new post.
We played the remainder of the game and not once did he utter a single word to anyone, not even the players who made it to third base. At the end of the game I politely noted that he had not coached the players and to let me know if he wanted to work with one of the real coaches in the future. He attended every game after that and never made a sound.
In life as in business the best way to silence a critic is to involve them. Sometimes they will jump in and surprise you, and you may have to eat a little crow and say, "Thank you." Usually, they learn enough about what's going on to realize they don't have a better way at all. But everyone benefits from the experience and it can bring a team together by removing the barrier of unfounded criticism.
So how did the giant of a miner react to the pie? He jumped up and knocked over his stool and screamed, "THAT'S MOOSE TURD PIE!... It's good though."