I just read this today. It’s helpful for clarifying some of the key differences Moltmann sees between himself and his contemporaries:
Political theology is not the same as ‘progressive’ theology, whether this be liberal Protestant theology or modernist Catholic theology. The differences and conflicts between the conservative Protestant Wolfhart Pannenberg and myself, or between the political theologian Johann Baptist Metz and the progressive post-modernist Hans Küng, are obvious. These others have never taken part in our initiatives and conflicts. On the contrary, they have often fought against us. Liberal theology was, and still is, the theology of the established middle classes. Political theology has its Protestant roots in Karl Barth’s anti-bourgeois theology, and in the experiences of the Confessing Church in its resistance to National Socialism. In the early peace movement of the 1950s, we always looked in vain for Bultmann and his liberal followers. As I see it, political theology is the true dialectical theology: a theology of contradiction and hope, of negation of the negative, and the utopia of the positive.
God for a Secular Society, 57.
Note that Küng is a close friend of Moltmann’s, and the two have worked together on various projects, notably various editions of Concilium. For the personal side, see the index and relevant sections in Moltmann’s autobiography. Also helpful here is Moltmann’s “Personal Recollections of Wolfhart Pannenberg,” trans. by Steffen Lösel, ed. by Jeania Ree Moore, Theology Today 72:1 (2015): 11-14. Finally, David Congdon’s The Mission of Demythologizing, the best currently available secondary work on Bultmann, has a section on Moltmann’s relationship to Bultmann and his critique of Bultmann’s politics (see the index). While I don’t agree with Congdon’s attempted defence of Bultmann’s politics, the short exposition is helpful.