In short, because of their two kingdoms doctrine, German Lutherans surrendered responsibility to teach God's law based on scripture. They tacitly enabled the Nazis to do all that they did. Contemporary two kingdoms theology calls for the same sort of separation between church and politics, McDurmon argues, and should therefore be rejected. 

It's a powerful warning based on a sobering story. However, it significantly distorts the history it purports to tell. McDurmon raids Pierard's article for his own purposes, describing German Lutherans in a way that endorses his own polemic. Yet the two kingdoms logic used to justify Hitler's policies was not the doctrine advocated by Horton and his Reformed contemporaries. And in fact, in most cases it was the church's active support for the Nazis' anti-semitism, not a supposed passive refusal to resist, which explains the church's actions in that tragic era. For a different picture, one might look more carefully at Pierard's article, not to mention the massive literature that describes Lutheran church history quite differently than does McDurmon.

So, what really happened?

Despite Luther's early two kingdoms theology, which implied that church and state could be separated (though Luther always insisted that both kingdoms, or governments, are under God and obligated to obey him), Lutheranism followed the reformer's later willingness to give magistrates a prominent 'emergency' role in church governance by developing a system in which church and state had complementary roles. Magistrates were to rule over the church and society, but consistent with the moral and theological instruction of pastors, and according to God's creation order. Early Lutherans would have been surprised to hear that the two kingdoms doctrine implied anything like a separation of church and state, let alone of Christianity and politics.

Many late 18th-century German Christians watched with horror as the Enlightenment spawned a revolution in neighboring France, its liberalism and anti-Christian ethos reverberating through Europe for decades. Napoleon's attempt to conquer Europe inflamed German nationalism and stirred Christian Germans to bolster their support for a government ordained by God and grounded in their religion. The concurrent rise of Marxism and revolutionary socialism only encouraged these trends. (For this and much of the information in the following paragraphs see, in addition to Pierard, J. S. Klan, "Luther's Resistance Teaching and the German Church Struggle Under Hitler"; Journal of Religious History 14.4 [December 1987]: 432-443.)

When Bismarck united Germany during the 1870s, he carried the solid support of Germany's conservative Protestants. Christians in Germany, comparing themselves to Marxists and liberals, came to see their country as somehow exceptional; that is, chosen by God to preserve Christian culture and therefore advance his purposes. During World War I, German clergy, like their counterparts in other countries, passionately and overwhelmingly supported the war effort. (See Victoria Barnett, For the Soul of the People: Protestant Protest Against Hitler [Oxford: Oxford University Press, 1992], 9-17.) When the victorious Allies forced the Treaty of Versailles upon Germany, along with a national admission of guilt, the Evangelical Church protested by calling for a Sunday of mourning. This religious observance continued through the 1920s.