What is wrong with Immanuel Kant's essay "What Is Enlightenment?"?

On your June 26, 2014 radio show, you mentioned that Immanuel Kant's essay "What Is Enlightenment?" initially seems to be arguing in favor of independent reason and political liberty, but that it really does not. I am confused by this. I thought that "What Is Enlightenment?" indeed praised independent reasoning and political liberty, encouraging readers to "dare to know." What is wrong with the case Kant makes in "What Is Enlightenment?"? In what manner does it fail to uphold reason and liberty?