my read is only if posts start getting censored beyond child porn / death threats / illegal activity
https://www.whitehouse.gov/presidential-actions/executive-order-preventing-online-censorship/
Depending on the terms of your employment, an employer can fire you for no reason at all (at-will employment).
Not wearing a mask would probably hold up as "for cause" unless you were the only one that had to wear the mask or something irrational like that. If it's company policy, yeah, very likely you'd have no recourse (unless it was only enforced vs. you). I don't see why you'd take the risk if it's company policy.
talk to a lawyer if you're actually willing to risk your job over the mask.
but you'd almost certainly have no recourse if it's company policy
most libs are fine with babies being murdered, Seth rich being murdered, justice Scalia being murdered, etc. I think if you figure out how to wake them up you win the war.