It's hard to tell with these Frankfurt districts. They may be artistic-alternative and run-down, but it sounds like they're well-off liberal-professional areas.
Heddernheim is known for its kindergarten designed by artist Friedensreich Hundertwasser, and Praunheim is known for director Rosa von Praunheim. You can find out more about him online.
All indications are that it's about anarchists . . .by 'x'Do you have any specific links to confirm this specifically for Frankfurt? I've read articles about the anarchist angle as it related to car-b-q's in Berlin and Hamburg . .. but not for Frankfurt. I'll check into the Friedensreich Hundertwasser, and Praunheim topics as time permits. Thanks.