Yes, im referring to the phrase you quoted above. I can give you sources but they're all in German.  says: "Das in Artikel 20 Abs. 4 garantierte Widerstandsrecht fällt nicht unter diesen Schutz, da es erst später in Art. 20 eingefügt wurde. Diese Ansicht ist unter Verfassungsrechtlern heute kaum umstritten." which means: "The right to resist that is guaranteed in Article 20 Line 4 is not protected by Article 79 because it was amended later. This point of view is not controversial among German constitutional law professors." 
 They cite as source "Grundzüge des Verfassungsrecht der Bundesrepublik Deutschland"(=Main features of the constitutional law of the Federal Republik of Germany) by Konrad Hesse who has also been a judge in the German federal constitutional court. I have also looked it up in the book "Grundrechte - Staatsrecht II" (=Fundamental Rights - Constitutional Law II) by Bodo Pieroth and Bernhard Schlink (marginal 1029) where they also say that Arcticle 20 IV is not protected by Article 79 III. They are also referring to Hesse's book there.