What are they going to do when someone else steps up and makes the same assertions with more tact? Fire him too? What about the person after them? They gave extraordinary leverage not to the person that they fired, but to the people that have not been fired yet.
It's uncharacteristically nontechnical of Google to think that of the anywhere between 30-50% of the US population that leans conservatively, there is only one of them working for Google in Mountain View and that any dissenting thoughts within the company will end with him, and that the liberal employees threatening to quit will be happy and sated just to see these few drops of blood.
It doesn't matter the size of the check Google cuts this guy, nor the next 100 individuals if they choose to also speak out. Google made a mountain out if a molehill, and they just left a very a long way for the snowball they just threw to gather some mass while rolling down.