No, you didn't read carefully. What is objectively moral or not does not depend on the opinion of the majority. It's true (ultimately, it's true anywhere) that the majority can ban things they don't like and call them "immoral," but that doesn't make them immoral in fact, and (as I said) legislating against something that is in fact moral is itself an immoral act.
I would suggest that criticism of the government is sometimes morally necessary, therefore, to ban all criticism of the government would be itself an immoral act. (Of course, the Constitution, as interpreted by the courts at present, does in fact permit some criticism of the government to be legally punished, e.g., a call for the violent overthrow of the government is illegal.)
Barring God himself speaking to us directly, the only way to determine what is and isn't moral requires fallible humans to make that determination. The system you've proposed would allow the majority to ban anything they consider "immoral."