Tell that to Joel Meyerowitz, Henri Cartier-Bresson, John Maloof (who handles Vivan Maier's photographs), Lee Friedlander, etc. then. If it is for artistic or editorial purposes, then you shouldn't need to worry, at least not in North America (or many other countries). What happens in Germany doesn't necessarily happen elsewhere. Even within Germany or other nations fiercely protective of privacy like France, people sell street photos as it is a vital art form and documentation of life. People can technically sue you for all sorts of reasons, whether or not they win is the more important angle.