1. I agree with you in as far as politicking that has nothing to do with your workplace can be a distraction, but as it pertains to Facebook the politicking is not abstract, but relates directly to Facebook's actions. It might be unacceptable for an employee to use company resources to boost a political candidate: this is not the case here. Facebook is curbing internal criticism of company policy.
2. I think it's disingenuous to imply that Facebook workers - and bear in mind we're not talking about the janitorial staff here, but tech workers who command salaries at and above $100K p.a. - must work at Facebook lest they be destitute. The greatest advantage of being a tech worker is the range of high salary positions available to you. That aside, I return to my previous point about this not being an abstract, culture wars style debate, but specific critique of company actions. It's not politics, but internal politics. Every company has internal debates about the strategic and ethical direction of the company - why not this one?
3. I understand that politics can be exhausting, especially in the highly polarized environment we live in, but I don't think that's sufficient reason to forbid internal critique of any company. Moreover I think the stakes are higher than we are comfortable with - Facebook has already ADMITTED that they provoked the Burmese genocide 2 years ago [https://www.nytimes.com/2018/11/06/technology/myanmar-facebo...].
To flip the question around: what makes YOU think that YOUR personal right to feeling relaxed at work is more important than an employee's right to ensure that they do not work on a product that can lead to mass murder? Moreover, is it really a political stance to demand that you are not complicit in unethical activity?