To much of  the Lutheran and Anglican world who have moved toward Arminianism and away from double predestination, or classical Calvinism, there is agreement with your main argument. I don't think anyone in your church is ignorant of the major theological differences with the Calvinist and Pentecostal  wing of the Reformation. Therefore talking about unity between "Protestants" as a general term, and Roman Catholics, is not productive.
 It does however make a useful cudgel for Catholic trads to bash any ecumenical efforts. These efforts have borne fruit when they proceed on specific denominational tracks. I think Kung is steeped in German, Swiss and European religious culture. Diversity existed for the first thousand years of Christianity. The Apostolic churches established in Asia (long before any western Franciscans or Jesuits showed up) by the hand of an Apostle, developed organically into churches with views not always consistent with the church of Rome.