That's a good point. I believe it's due to the fact that American-style conservative views are so fringe in Europe that no one takes them as a threat no matter outlandish they are. But in many European companies, signaling yourself as a supporter of the local far-right party (whether it be the AfD or the FN or the SD or whatever) can be grounds for blacklisting and ostracization. Still, the question remains: does that make Europe a monoculture?
I think that outlawing hate groups and proscribing their speech is an appropriate function of the state. It's an instrinsically public, political function. That's why it shouldn't be done by company management: it rightfully falls to a democratic institution that's accountable to the whole of the public.
