YOU were reading Bohnhoeffer. No one else in this discussion seems to have been. If I were reading something about his ecumenical joining of the Body to that which is against Christ, I would have the very same objection as GOD says to not do it.
From the book:
The man counted among his friends a number of prominent persons, including George Bell, the bishop of Chichester. Bell arranged the [memorial] service, for he had known and loved the man being honored [Bonhoeffer]. The bishop met him years before the war when the two were engaged in ecumenical efforts, trying to warn Europe against the designs of the Nazies, then trying to rescue Jews, and finally trying to bring news of the German resistance to the attention of the British government.
from Bonhoeffer: Pastor, Martyr, Prophet, Spy