"I don’t work for Google, but I do know that most big companies have established channels for addressing employee grievances"

If you read any of the articles coming out of this event you'll see that the protestors tried for months to get a dialog going with management in half a dozen different capacities, all of which were denied or swept under the rug immediately. Due to this behavior from management, many of the employees engaged in this cause had decided to quit, but if you were one of them why not try to protest one last time? This was basically the last option they had prior to leaving