While I think this woulndt hold up in court, the whole process till getting there can be very intense, nerve racking etc. It couod take years for this to go to court or for the person getting notified of the dismissal of the case.

Also their name might get put on lists that collect identities of suspected extremist, which can influence their future interactions with the cops and also can influence their job chances.

Also getting arrested by these violent thugs itself can be a very stressful and unpleasant experience that can have an effect in their willingness to stand up for their opinions.

These possible results are usually ignored by german courts.