Everybody likes to complain clients -Al Bundy at the shoestore, the backroom Congress, heck, even clients complain about their own clients. This is human nature.
A little while back we worked on project where our client made all the wrong decisions and allowed their client to make even worse ones. At every point we offered our recommendation, sometimes they were taken, sometimes ignored. While we may have thought they were "stupid" or "making the film worse" we executed the project cheerfully and to the best of our ability.
Why? When you know everyone is wrong and you are right? When you're the animator/designer/layout artist/compositor/whatever and the director is an imbecile? Why put up with it?
There's an easier answer to that. It's the answer to another question: What is my job?
If your job is to complain then, by all means, gripe away!
We see our job as making films. The only thing we can control is getting the piece completed. If the client has dumb ideas, if they're constantly un-approving or changing things, if they have no clue what their own job is -that's out our purview as producers.
Focus on your job, what you're supposed to do. Anything else should fall into the very large "not my problem" category.