THE FOILING OF AN Islamist terrorist plot this week in Germany is noteworthy for several reasons that may not have been obvious from the headlines. The first is the involvement of an ethnic Turk. On Tuesday, police in the German state of North Rhine-Westphalia seized three men identified as a Turk and two German converts to Islam (under German court rules, their full names were not released). While the activity of converts in terrorism is not new, the Turkish community in Germany has so far been free of the plague of religious extremism. Turkish and Kurdish immigrants to Germany and...