There are lots of things that you're not supposed to be fired for, that people get fired for. Unfortunately, the onus is on the employee, with almost no resources, to prove that the company was lying.

Sure, you can't be fired easily. But what about when it comes time for a raise or promotion? What about when you are interviewing for your next role? It's hard to imagine anyone getting punished for discriminating in these cases, since it's always easy to pin it on other things.

This is not how reality works at all. You're fantasizing.

They fire or sideline you for something else and you never get a job in that industry again.

And if you want to fight it, it's you vs. an army of corporation backed lawyers.

if you really can't be fired, you surely won't be doing any actual work ever, even if you still get paid.