How do you reconcile this against the fact that extreme anti-establishment parties are surging throughout Europe, including in places like Germany that have some of the most extreme restrictions on speech? For instance Germany is now even considering trying to ban the AfD [1] (political party) who are now polling at > 20%, which is quite high in a functional multi-party system - higher than Olaf Scholz’s Social Democrats party. Incidentally 47% of the country supports banning them, 47% oppose it. There have also been numerous instances of violence against party members, and more. And there are similar divides in many other European countries.
The one thing I'm certain of is that we're all living through a major inflection point in history, for better or for worse.
European countries have a history of assimilating anti-establishment parties into the establishment. They did it with revolutionary communists, they did it with the green movement, and now they are doing it with the conservative nationalist / right-wing populist / whatever parties. The Finnish equivalent of the AfD is in a coalition government led by the traditional center-right party. In Sweden, the corresponding party supports the right-wing coalition. And in Italy, Brothers of Italy is the leading party in a coalition that turned out to be unexpectedly moderate.
I think here you're talking more about what eventually will happen, while your earlier comment (and the one I was responding to), is more about what is happening. The fact that the polarization may end up playing out better than in the US (though the situation in Germany as of yet gives no indications of that) is a different issue than the fact that there is an undeniably sharp rise in polarization, even in places with stringent speech controls.
In my experience, polarization has been in decline in Europe for a few years. It started rising in the aftermath of the financial crisis and the refugee crisis, but the farce around Brexit and the Russian invasion of Ukraine tempered it. People are again willing to work within the system rather than trying to replace it with something radically different.
Germany is a bit of a special case due to their history. They still can't cope with anything that looks even remotely similar to fascism.
But it's not really "Germany" calling the AfD fascist, in fact ever more Germans are voting for them. Rather the people who don't like them are calling them fascist. You're effectively describing an effect of extreme polarization, where 'the other side' is demonized in ways with, at best, tenuous connections to reality.
I think your post hits on the primary cause of polarization: incompatible ideologies. One group in [some country] want ever more immigrants, regardless of the cost or quality. The other side wants to limit immigration to skilled and educated migrants who are expected to learn the local language and integrate into society. These two sides' views are different enough that it's pretty tough to get a meet in the middle, and the issue is relatively urgent, so you get polarization.
Of course this leads to nasty online conversations where you might have one group talking about the crime rates of new migrants, while the other side calls them racist or fascists for doing such. And I would agree that this probably contributes to polarization, but it's also an effect of an already existing polarization, rather than anything even close to a core cause. Europe's had no difficulty polarizing plenty throughout history, long before the internet. It's just for the past ~80 years we've all been living in a little bubble of relative peace, tranquility, and growth. And I think that bubble has popped.
The one thing I'm certain of is that we're all living through a major inflection point in history, for better or for worse.
[1] - https://www.telegraph.co.uk/news/2023/08/13/afd-party-ban-ge...