He is probably talking about the perception regular customers get of your profession. You could be a graphic design god, unless you really play the role of such god and demand a god's salery, every incompetent middle manager will believe they have more expertice than you, bike shedding all over the place.

This rarely ever happens if you are a developer interacting with similar people (e.g. as a freelancer). They think you are some kind of magician. Similar when you are a good audio engineer or something, they will just let you do your thing.

The funny thing is: this perception is completely independent of the quality of your work. They will always have something to say – sometimes even stuff that makes sense, but very often just for the sake of it, with no real reason. Everybody thinks they have a good taste and a great eye and what kind of graphics are needed, while in fact often they have none of the above.