I question your reading comprehension. It’s much easier to claim something causes harm than to demonstrate it would.
History doesn’t support your assumptions: recalling the civil rights & free speech movements in the US, civil rights advanced despite similar free speech constraints I’ve advocated (eg, clear & present danger or imminent lawless action standard) and despite a harsher environment with Jim Crow laws and white supremacists speaking freely. Civil rights can advance with such narrow restrictions on free speech and have before when circumstances were worse.
Where would ancient Greek democracy fall in this spectrum?