Bannon doesn't like Traditionalist Catholicism because he is at all pious.  He has been divorced three times and I doubt that he attends Mass regularly.  He seems Traditional Catholicism as a means to an end because characters like Burke agree with him about the decline of the West and the dangers of non-white, non-Christians.  Traditionalist Catholicism is a perfect place to fish for converts to the alt-reich.  It is paranoid and inwardly focused, antisemitic, and conspiracy theory driven (see Fatima). It is interesting how easily the Vatican II hatin' set like Rorate Caeli and Father Z have taken to being shills for the alt-reich, Trump, and Russia.  

In fact religious fundamentalism of all stripes attract bigots because they cater to these people's hatred.  ISIS and the alt-reich are the same.  Both give the same dark message of hate and scapegoating to their mainly male followers who want someone to blame for all the problems in their lives.