I have encountered clients who have no experience in marketing and publishing, hire 3L Publishing (www.3LPublishing.com) to publish their books, and then argue with the team about the process. If you're going to hire experts who have done something that you have no experience doing, the idea is to listen to the experts.
Now the customer is always right, true. Problem is when the customer thinks he or she is right -- and their idea of right is simply wrong. When you're talking about writing and editing, and the customer's ultimate goal is professionalism yet they're not following expert advice and experience then the end result is not always professional.
When it comes to writing some writers don't want their work touched no matter what the edit. I was joking with a friend of mine that some writers argue about grammar. My go-to solution is to not only explain why it's wrong, but also back up the answer with my favorite website Grammar Girl (yes, that's a real website). When Grammar Girl becomes my source for the argument because the writer isn't listening, it seems ridiculous. You now have a trust issue going on. Your client obviously doesn't trust your expertise.
My piece of advise: if you hire experts, trust your experts. Unless you've done what they're doing for a living then you need to listen. Their experience and knowledge should supersede your belief you know better. Chances are you don't know. And chances are your end result will not be professional. Of course in those cases the client inevitably blames our team for those mistakes produced from lack of listening.