For example, Dr. A wants to do XYZ, and I have to give an emphatic NO because what he wants to do will violate at least 3 regulations and could result in a huge fine from the OIG.

That was a real scenario, but for the most part, if I have to say no, I explain why I can't do exactly what they want, and I try to help them find alternatives. So when the answer really is no, they may grumble, but they know that I'm not just saying no because I don't want to go to the effort of implementing their idea.