There’s two sides to freedom. Freedom of individuals to express themselves, and freedom of companies, which are also made of individuals, to want to work with each other. I personally think all employment should be truly at will on both sides.
Life isn't fair. But we as a society do what we can to make life more fair. And I personally believe that it's more fair to ensure people aren't forced to choose between expressing their half-decent opinion, shitty jobs, and homelessness/emergency-only medical care/low-quality food/whatever else you would probably deem "essential", than it is to ensure bosses can hire and fire whoever they want for whatever reason. You can disagree, but I think most people do agree, considering most people are also working jobs and would be in danger of losing their essentials if they were fired (as apparently 62% of Americans are living paycheck-to-paycheck).
There are other solutions too. I think if we had UBI, or just better unemployment and an economy which guarantees you a decent job provided you can do decent work, unions and employee protections wouldn't matter. But currently it seems like those reforms are far away, while unions and employee protections exist right now.
We use a bit of asymmetrical freedom here in the US; we don't FORCE anyone to stay, but we don't allow you to bar people from being present without a good reason. And in general, "at will" employment is the norm and this is a special case; it's only when a company shows that it is incapable of being reasonable when stuff like this happens.
They forfeited the control over their employment by being irresponsible, by being incredibly unprofessional, by holding employees to personal standards outside of professional bounds. They stopped acting like an employer, so they lost the benefits that come with that status.
A company isn't just a bunch of people who want to work with each other, unless it's structured as a worker owned coop, partnership, or similar. More often than not it's a legal institution created for the express purpose of extracting profit by extracting value out of poorer people's labor. There's no inherent "freedom" for any such entity, only what society chooses to give it.
Some laws are meant to bring fairness at a time of egregious unfairness. But don’t need to be laws forever. That doesn’t mean the problem will inevitably return without enforcement.
Someone isn't fired via democratic fiat of the entire "company" organism.