We have a number of tiny fringe groups like this in the US, such as the Westboro Baptist Church, which would surely be illegal in most of Europe. I will defend their full right to speech so I can have my full right to speech.
In Europe, free speech laws shut down leftist activists, not just "white supremacists, racists, fascists, extreme wahabists/salafits". I think this is a strawman and an idealistic vision of being able to control speech fairly. One of the biggest active groups is the IHRA, a Zionist organization. The IHRA consists of 31 member nations including the United States, Canada, Australia, France, England, Germany, and twenty-six other European countries.
They are essentially criminalizing Palestinian activism. See https://socialism.com/statement/defend-free-speech-stop-the-....
This has become a big problem in Germany for Palestinian/Muslim activists who are critical of Israel. Curtailing free speech is a slippery slope.
Now, perhaps the AfD will be banned in Germany, as it has been placed under so-called "Verfassungsschütz beobachtung", an agency that protects the German constitution. Should it be criminal to identify as a communist or nationalist in Germany? What comes after that — perhaps it should be criminal to be a Jew or Muslim or Christian, given the hateful teachings of the Torah, Quran, and Bible?
This is a bad line of argument.