" and that most of the suspects were accused of posting anti-Semitic, xenophobic, and other extremist messages"

Laws that stop this kind of "expression" have existed in Germany a while now, for historical reasons.

I disagree, violence is not just physical, verbal abuse can be a form of violence as well. What kind of idea is public hate speech expressing?

From the article, "Attacks on refugees are often the result of radicalization, which begins on social networks."

I don't really think that calling to arms (in this case as self justice in combination with using Nazi symbols) is expression of free speech. It is totally okay that our understanding of free speech differs, but I just don't count that as free speech. And sympathizing with Nazis by using their symbols is not okay for me, too. I might be wrong, but in a lot of countries it might not be legal to call for self justice on a whole race.