They don't call their firing consequences, they call it retaliation. They end the video by declaring that they should all be reinstated because they did nothing wrong.
Loads of internet posters very strongly and emotionally declared that they all knew that they'd be fired, including in this thread. That they were professional martyrs who heroically gave extremely desirable jobs for a cause with eyes wide open, and of course they knew what would happen. But every bit of evidence from the actual participants betrays the opposite.
And we're going to see the same sort of rhetoric as college students start getting expelled, their academic careers ruined. You'll have the former students on one side crying and gnashing about how unfair and unearned the consequences are, and on the other side third-parties cheering on their self-sabotage as heroic.
A huge challenge in general is that a vast majority of us, myself included, only get fed headlines online and assume we know the whole story. I try to caveat it with "if this is true, ..." to try and help control that unknown.
Well, it is retaliation. The consequences were retaliation by Google. It's maybe just not prohibited retaliation under the law.
IMO it'd have to be something related to whether the response from Google could have reasonably been expected given the rules, employee agreement, etc. If the protests were disrupting others from getting their job done, that seems pretty reasonable to me personally. Otherwise I guess it would come down to how strict Google has historically been for people ducking out of work without notice (that's the best I could see Google claiming if it really was a peaceful protest / sit-in).
At least for me, I can't speak for others here, its a combination of either not thinking it through or purposely making a spectacle out of themselves just to make a spectacle. For better or worse, I don't have much patience for people making a loud show of themselves and appearing to act irrationally (ex: protesting the company you work for, acknowledging you may get fired, getting fired, then filing a complaint presumably to get your job back?).