The employee, as a white male in tech, is absolutely morally right to use his privilege to call out other powerful white males for their silence.
And make no mistake, silence is complicity. Many smart philosophers have written about this, see MLK Jr. or Maya Angelou for more.
This is the core of being an ally. Use your privilege to make the hard ask from your peers that a less privileged person, who is decidedly not a peer, cannot.
FB, on the other hand, is also right in a different sense, to maintain internal expectations that singling out colleagues with your political opinion in public is ineffective at best and toxic harassment at worst. FB are signalling to the rest of their employees what behavior they will not tolerate.
In the end, this employee leveraged awareness several orders of magnitude more than had he not been fired (and will likely easily find a new job) and FB protected whatever they believe their culture to be (and whatever other HR lawsuits they believed themselves to be at risk for).
This isn't silence though, this is rejecting an order to partake in a protest.
Even if it is silence, staying silent is still a right.
Harrassing people for silence is akin to harassing people exercising their freedom of speech.
Looking at your profile, I can point out countless atrocities that you don't explicitly denounce. Do I see you upset about how Israel has amped up its program of settler colonialism in Palestine in the past few weeks? How the PRC is running literal concentration camps in Xinjiang? Or, moving along to the USA, how men have extraordinarily high suicide rates? Or how the elderly are being sacrificed at the altar of economic growth in the midst of COVID-19? Or, thinking long term, the tens of millions of people who will die because of climate change?
I don't. And, for what it's worth, I wouldn't be surprised if you have "correct" points of view on all of those. But you're still being complicit in deprioritizing those things and prioritizing your own set of causes, at the expense of human lives. And if you're indeed complicit in a conspiracy of silence on them, you've got blood on your hands.
Brandon Dail was demanding someone add some kind of explicit support for BLM to a Github repo. Where does that stop? I can think of hundreds of very worthy causes that need more publicizing. Is what we ultimately need some long list of evils that every open source project needs to denounce before right-thinking people can choose to use them? And, if you choose to use e.g. Linux, can I denounce you for choosing to use software that is complicit in a conspiracy to terminate black men's lives?
People can prioritize and take action on different causes in whatever way they want to. It's fine to ask individuals to reprioritize, but you're not entitled to anything. And, tactically speaking, ever-increasing stridency of tone and denunciation of imagined enemies is not an effective way to gather support for a cause.
As for Dail's victim, you don't know whether he has or hasn't helped in his own way. This Dail guy wanted to coerce a coworker to do something that RISKS HIM GETTING FIRED. He said no to Dail; this doesn't mean he hadn't or wasn't willing to help.
I don't like FB and I hate Zuck's stance, but no company would allow someone like Dail to continue bullying coworkers and creating a hostile work environment. I wouldn't be surprised if he already had a list of prior complaints. HR doesn't usually fire people based on a first-time offense.
If you are ever in charge of fundraiser or are looking for people to join a worthwhile cause that you support, try to understand that you'll gain more allies if you're not shitting on & shaming people to do what you want.
This is needlessly reductive and unhelpful. One can work to end racism and police brutality without supporting groups like BLM and/or making public declarations about the issues.
So, no. Silence is not complicity.
What threshold must you cross (in terms of platform size) for silence to equal complicity? Since it apparently doesn't apply to you, but it does apply to a GitHub repo.
Once you've made up your imaginary platform size threshold, which movements must people not be silent on, lest they find themselves complicit through silence? Is it ALL political movements? Those READMEs are gonna get pretty long if so. Is it only the "most important political issue at the moment" that needs to be voiced? Who decides what the most pressing issue is? Is there some sort of vote going on that I don't know about? When is it OK to start being silent again? If he puts up a BLM message in his repo and then takes it down the next day, is that OK? Or does he need to keep it in there forever (because presumably Black Lives always Matter, so he should keep it in there indefinitely, right?)
There are way, way too many things going on for silence to mean complicity.
Take any other humanitarian crisis, and ask yourself if anyone silent must be complicit. Think about it for a second. It's just not true. If someone in Germany were to not speak out against the Nazis rounding up Jews, but at the same time was hiding Jews in their basement, would that person be "complicit" in the Nazis crimes?