Locals. Yeah yeah, white man good, others bad! My experience is that the native youths don't give a shit, meanwhile people who sounded/looked foreign cared more about cleaning up after themselves. And in Berlin I had to yell after 2 Germans who just stood up and left their disposable coffee cups on the street bench they were sitting on.

Caveat: we're probably both suffering from https://en.wikipedia.org/wiki/Confirmation_bias .

You're right. I was stressed yesterday. There are filthy people of all backgrounds. I just happen to live in an area where people are both dirtier than average and not German. If I lived somewhere more German, I'd probably have more examples of German people doing dirty things.