In my opinion, condemning the Zionist movement as "nationalistic" is unjustified. Consider the path by which Herzl came to his mission. Initially he had been completely cosmopolitan. But during the Dreyfus trial in Paris he suddenly realized with great clarity how precarious was the situation of the Jews in the western world. And courageously he drew the conclusion that we are discriminated against or murdered not because we are Germans, Frenchmen, Americans, etc. of the "Jewish faith" but simply because we are Jews. Thus already our precarious situation forces us to stand together irrespective of our citizenship.
Zionism gave the German Jews no great protection against annihilation. But it did give the survivors the inner strength to endure the debacle with dignity and without losing their healthy self respect. Keep in mind that perhaps a similar fate could be lying in wait for your children.