In the best consulting relationships, both you and the client have the freedom to be yourselves. Because the consultant operates from outside the organization and have less “skin in the game,” they don’t need to hide their real thoughts or feelings behind a curtain of politics or politeness, and neither does the client.
This is not just a personal reward for the parties involved, but rather an intrinsic part of the value delivered by the consultant: often, organizations will bring in an independent consultant not necessarily because they have superior expertise, but as a way to expedite truth-seeking.
However, note that authenticity is earned, not demanded—and this goes for both sides. Both the client and the consultant should do the work required to establish psychological safety, but they should leverage the natural advantages of the consultant’s position as leverage to make the process easier.