The "they should've called the police" argument is legally wrong in Germany. The allies were pretty pissed off after WW2 and wanted to eliminate the "bystander" excuse for people who watched Jews getting gassed. That's where the "failure to render aid" law comes from. Of course, you're not expected to endanger yourself, but - say, there's an average guy assaulting someone, and you're travelling in a group of 5 reasonably muscular, capable guys... your excuse to not step in is gone.
It doesn't seem that the "aggressor" here was very aggressive and remained largely passive. No laws are absolute and that's what judges are for.
I doubt the "failure to render aid" law in Germany is interpreted as everyone is deputized to enforce every law, everywhere, at all times. There's probably a narrower view on what's appropriate and when.
(More related to the actual events) if someone illegally parks their car in your driveway, you should call the police to have it cited and towed. You can't break the windows and try to move it yourself under normal circumstances. However, if there were a fire and the car were blocking some sort of escape, then sure, break the windows and drop the parking brake to get the car moved.
Again, this is why we have judges and you should call the police in almost every case except those involving grave danger.
The "they should've called the police" argument is legally wrong in Germany. The allies were pretty pissed off after WW2 and wanted to eliminate the "bystander" excuse for people who watched Jews getting gassed. That's where the "failure to render aid" law comes from. Of course, you're not expected to endanger yourself, but - say, there's an average guy assaulting someone, and you're travelling in a group of 5 reasonably muscular, capable guys... your excuse to not step in is gone.