@19p If a large group of you all have enough savings (safety net) to leave, on the day they do that, turn in 2 week notice (or no notice if you are not concerned about that decision following your career). It will send a big message. In reality, it may not accomplish much.
But a large numbered walkout on a specific date, given the specific reason sends a large message. Not to mention, increases your all’s chance for a successful class action lawsuit.