Feedback and constructive criticism, gently delivered—what Patrick Lencioni calls the "kind truth" in a slightly different context in his recent book—are like magic. It shouldn't be personal, or taken personally. The objective that you and your team of reviewers are working toward is to make whatever you're doing better. Be it a product design, a business plan, or content marketing copy.
Here's a non-client example. Our minister recently asked me to take a look at one of our church brochures. I looked it over and noted some redundancies and inconsistencies, pointed out some opportunities to simplify and make stronger statements, and marked some stylistic and copyediting issues. She thanked me profusely for my feedback, before pushing back with some other ideas. We went back and forth over several days until we arrived at words and a structure and a design that were much clearer and potentially more effective than either one of us would have come up with on our own. That's the magic. That's how it's supposed to work.
This post falls deeply in the execution category. Execution is where many content marketing efforts fail, or fail to achieve 80% (to throw out a number that's probably on the optimistic side) of their potential.