With that said, I get the sense there is a large part of a story that is not being told here. Where was the manager? Has this employee had a history of maintaining appropriate professional boundaries with respect to communication? If Facebook doesn't have the appropriate paper trail, they could easily be sued for retaliation.
Possibly personal opinion here, but given the current charged (understatement) political environment and twitter's propensity for "scarlet lettering" people via mob harassment, I don't think this was borderline. This seems like a deliberate attempt to get a large group of people to harass a co-worker because of differing opinions about how and when to communicate political opinions.
- The former employee may have genuinely thought that a public "conversation" could result in a positive outcome (perhaps believing "sunlight is the best disinfectant")
- The two may know each other previously - perhaps the former employee may have felt they had more of a mutual level of trust/familiarity than they actually had?
- The former employee may have been wanting to leave Facebook anyways and (cynically speaking) wanted to go out in a blaze of glory and resign in a high profile manner
- The former employee may be neurodivergent in some way and have difficulty navigating the subtle boundaries of spaces of privacy that exist along the spectrum of 1:1 to effectively "in public"
- The former employee, frustrated and angry and activated by the heat of the moment, willfully decided to sic the mob on the other person
Honestly, I don't know this person so it's hard to say. And I do know it is often the case the hindsight is 20/20. But, I wonder, in this former employee's entire time at Facebook, did their manager ever notice any of these kinds of aspects in that employee's interpersonal interactions or collaboration style? In my experience, hints of these things surface fairly quickly in the workplace, especially during the ramp-up phase or the first time some sort of an adverse situation is encountered, whether it be subpar code, a deadline that doesn't make sense and is hard to change, or a stakeholder that isn't exactly aligned with reality and isn't very easy to get there. If this former employee (consciously or unconsciously) takes such an adversarial approach to conflict resolution with a colleague, one wonders if this was the first time they have ever done that, or merely the first time they ever did this to such a degree.
But who knows. The past few weeks and months have been insane. Many people are seeing more psychological stress and social unrest now than they've seen in their entire lives. A lot of them are not prepared to handle these kinds of situations in a manner they won't regret. It's unfortunate that it has to turn out this way, but on the other hand, this kind of behavior really can't be condoned. It's emotional blackmail.
I really hope this former employee takes to heart a valuable lesson from this, but I have a feeling that the exact opposite will happen; to be fired so publicly, with the humiliation that comes with that, is the perfect accelerant to a radicalization that might already be in progress. I don't know where we go from here.
On your last point: This is what I fear most as well, a permanent radicalization of this individual.
One important principle in management is that you must be extremely careful NEVER to humiliate someone in even the slightest way in front of audience (any meeting >3 people by my book). The mere suggestion that "something didn't go well" can trigger extremely hurt feelings, defensiveness, and antipathy depending on the size of the audience.
Well on the internet, everything occurs in front of potentially infinitely large audience. To admit that you are wrong is to endure humiliation before the whole world. To deal with this, people dig in their heals, and claim that "I was always right, and those who disagree with me are not only wrong and stupid, but evil to the highest degree."
It's heartbreaking watching watching the far left stab their nearest ideological neighbors and most important allies.