From what I understand of the attacks in Cologne, these events seem to be more similar to actions carried out by criminal gangs (it is not unheard of for street gangs to carry out harassment or attacks on mass on women, whether in the US or in other countries around the world). I am aware that in France, for example, those of Arab or North African descent often suffer widespread discrimination in areas like employment, housing and policing, not unlike what we witness among African Americans in the US, or among aboriginal peoples in Canada. The social consequences of such social problems are therefore apparent -- higher crime rates, higher incarceration rates, prevalence of street gangs, drug problems, etc. The situation may be similar in Germany as well.