First, I don't think that, in this situation, the client should be in direct contact with the developers. I'm not sure how the situation is (if the developers a

First, I don't think that, in this situation, the client should be in direct contact with the developers. I'm not sure how the situation is (if the developers are physically working at your client's location or not), but I think all questions and remarks go through you, since you are the project manager. They will probably give you a lot of shit, but I think that one of your responsibilities is to shield the developers on the project from this kind of shit. Also, I would try to communicate that the client probably is an expert in their business, and your developers are not. At the same time, your developers are experts at developing, for which you need to know an enormous amount of details about the business. If they seem idiots, it's because they lack domain knowledge (and it might be worth it to try to do something about that in cooperation with the client -- I'm not sure he's open to this but you can always ask him for suggestions on improving domain knowledge). On the other hand, don't give the client any reasons to be an asshole. Underpromise, overdeliver, and communicate timely and clearly.