If you are attacked by Police there is two options. Get beaten up and be called violent for resisting arrest or get beaten up slightly less by fighting back and get called violent.

The goal of the police, the nationalist mayor of Berlin (he thinks the name of someome should be deciding about who is a "real" German and who is "only" a German citizen) and the authoritarian interior ministers is to beat the protestors up so much, that they stop protesting. It is a classic authoritarian violent repressive strategy. They tried to get the courts to ban protests altogether, but the courts aren't put in line yet. There is complicit media outlets, similar to fox news in the anglosphere.

There is people who seek fights as a form of protest in Berlin, but this is in non announced actions or after the police violently ended announced demonstrations. There is videos of these where they shoot fireworks and put barricades on the streets. But these are very different from the regular protests and i would be extremely suprised if Thunberg has anything to do with these.