The "liberal with the truth" bit isn't about the ability to exit; it's about the EU being "externally controlled". The EU is an organization of which each Eurozone member is, well, a member. They have votes in the EU Parliament and European Council (the latter is responsible for appointing the ECB president) and a say in deciding the membership of the Executive Board.

(Indeed, the German Constitutional Court generally rules on the constitutionality of power transfers to Brussels based on the degree to which the control of said powers is democratic.)