This is the cost of being free, not everyone likes it, but it way better than the alternative.
I don't think it is a more violent society. Maybe in the discourse, but not in actual crime. And yes, people are more polarized, but I think it is tied more to the economic context than anything else.
The party thing was in the Eastern bloc, not sure where that is now the case.
But this aside, did the murder rates increase in the last 10-20 years, decreased or is it the same?
US rate is a little bit up from early 2010s, but a lot lower than in the 1980s, in the EU the rate was low in the early 2020s compared to the previous ten years.
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...
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.
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 EU" is not equivalent to "France and Germany", despite what they think.
Nazism as an ideology is illegal to promote in Germany. Use of Nazi symbols outside of an artistic or educational context is illegal in Germany and France (most European countries really). Several neo-nazi, neo-fascist, and communist parties have been banned since the founding of the modern German state. Far-right parties in Germany are always walking a fine line - if their membership flirts too much with nazism or fascism they are very much liable to be banned.
Several European countries with strong democratic traditions in the modern era remain very wary of extreme ideologies. Their proponents murdered millions and burned the continent to the ground less than a century ago. Most people are comfortable with the state killing these movements in their infancy.