Not difficult at all but perhaps they in Belgium don't have the culture that they as employees are not just grateful serfs under the holy entity of the employer, so they might think they can speak in an open and free manner about subjects like possibly getting a pay rise or change work place at some point.
OK. So if you want to be pedantic replace "employed by" with "under contract with" if that doesn't upset your sensibilities as much.
The point remains the same! You can say something without saying hardly anything at all whilst not risking upset the person / organisation that you have entered into a contract with.
It's akin to me spending my lunch hour standing outside my office with a sandwich board with "GIS A JOB" hanging round my neck. It's just not done. (although perhaps it is in Belgium & Sweden )