The issue was that tying political opinion to jobs was what the Fascists did in the 1930s. So it's kind of a "Never Again" category. It isn't entirely enforceable but companies cannot use it to fire people based on private conversations about politics. This has come up a few times where I work actually and the answer is the same. That's off the table.

No stranger than religion, when you think about it. Both are completely arbitrary (a personal choice), people get very emotional and defensive about them, and they seem irrational if you don't share the beliefs.

I assume "political opinion" as in "the way you vote", not so much speech about politics (which would just be protected by rights protecting speech.) Even in the US, you have a right to voting in a way that's protected from others' observation.

Or, to put it another way: if you want to hold a political opinion, and then express it by voting, but otherwise keep it completely secret from your community... that's your right.

A useful way to think about this is that the Supreme Court ruled the state cannot punish someone for advocating genocide in the abstract at a KKK rally, not because advocating genocide is somehow a natural right or that free speech is absolute, but because the government had previously exceeded its authority by going after political dissidents (particularly Communists) using similar logic. So free speech protections in the US for hate speech are a reaction to state abuse in the context of the US.

In Europe the abuses were different so the protections are different.