I've been on the receiving end: being told what my UX designer thought I should know.

The message was: "shut the hell up and listen, and stop putting decisions that should be mine to a democratic vote." I did both, and our product improved greatly as a result.

We added a UX person to our team after the project was already underway and a first prototype was already out, and until then, I'd been practicing a somewhat democratic style of management: we'd discuss design issues informally, come up with options, ask our graphic designer for comps, and vote if we couldn't generate a consensus on the resulting choices. At the time, we didn't have much user feedback to steer by.

When the UX person joined, I continued my style. Bad idea. The person very diplomatically let me know indirectly, and I am glad that happened. The rest of us stepped back significantly, and began keeping discussions to use-case level, leaving it to the UX person to decide when to escalate specific visual decisions to the group level, what comps to generate, and when systematic user testing was necessary.

I still occasionally override and do some micromanagement when there is a very real need, but I keep it to an absolute minimum.