The comment you're replying to wasn't meant as a comment on the case, but to rebut the idea that "at-will employment" is some sort of universally-valid, natural state. It's just one of many possible answers, and every society has come up with their own.

Regarding discovery, I must say that the US system is actually more advanced than Germany, where, in civil law, there isn't really a doctrine for recovering incriminating evidence (or otherwise compelling evidence) from the opposite side, apart from a few specific circumstances.