This quote is from his correspondence with Ian Brown taken from the L’Arche website:

“Christians, however, can be infected by nationalism and by an attraction to the heroism of war, to the so-called just war. Pacifism, manifested in a special way by the Quakers, the Methodists and the Catholic Worker communities, is not just a refusal to fight in war.  It is a way of life, where love is put at the heart of all things. It is a struggle to bring peace and to resolve conflicts at all levels of society. It is to stand for truth and forgiveness.”