Bangladesh, May 6 -- Germany has crossed a perilous threshold. The countrys domestic intelligence service, the Bundesamt für Verfassungsschutz (Federal Office for the Protection of the Constitution), has officially labeled the Alternative for Germany (AfD) a “confirmed right-wing extremist” party. While not a formal ban, this classification moves the AfD closer to complete political exclusion, creating risks far graver than the government and its allies seem willing to acknowledge.

This act is being justified on grounds familiar to Germanys political culture: the need to defend the democratic constitutional order, to uphold human dignity, and to protect society from extremist threats. Yet in reality, it looks suspiciousl...