Afghan pride and German prejudice

The incident happened in May but Hamburg's Afghan community is still in shock. Hamburg has the largest population of Afghans in Europe, but so far they have lived inconspicuously. Afghans are among Germany's better-integrated ethnic minorities. Some 40% are German citizens and the community values education. So what went wrong? Why did Ahmad feel compelled to kill his sister when in Afghanistan men like Perwez Kambakhsh risk death by challenging traditional perceptions of Afghan women?