The boot-licking in this comment is seriously professional grade.

Everyone who gets fired says they were fired ‘illegally’

The person fired isn't the one saying it. The National Labor Relations Board is saying it. The NLRB is a government agency. They don't take companies to court just because some employee is whining, because if they keep making too many failed claims they'll have to answer to Congress.

You can’t do that. If you’re given direction and a co-worker tells you to not do it, they are being insubordinate. That’s 100% fireable

This isn't the case even in most of the US, despite the general hostility to workers right in the US. Seeking to organize demonstrations against material changes to working conditions is generally protected. Employers can not on a general basis prevent employers from debating working conditions and reactions to that, up to and including organizing reactions against it.

You'll note that their excuse was not insubordination according to the lawsuit, but a breach of a company policy, because even they are not dumb enough to think they'd get away with claiming this was due to insubordination.