At the latest in court. Otherwise, it’s just statement against statement, and in Germany it still applies: "Innocent until guilt is proven."
Sorry, but you’re just mixing up some terms here arbitrarily and wildly, just to make it sound nice—from "typical German" to "statement against statement." In a school test, that would be "off topic" plus "fail."
If a disturbance exists, no further steps are necessary, with or without court, or is murder only forbidden starting from double murder?? Oh dear....
This is not about the classical form of guilt...
Somehow this sounds like TV courtroom show sofa knowledge à la millions national coach.
Here, a person feels strongly disturbed and impaired by excessive use of their speakers (see e.g. higher regional court ruling). And....as wonderfully explained, not everything is okay that is not explicitly forbidden. His "letting loose" interferes with the life of another. I had also referred to the definition of "room volume."
As nicely describes, it often has something to do with decency and social behavior. But then again, you can’t buy that at Aldi or get it as a free subsidy from the KfW, although that would probably be a more sensible solution than some others.
Here, someone feels bad and then has to read that the neighbor is right with his speakers, and that the woman should just stop making such a fuss. That already drips heavily with spite.