Originally a conformist cleric, Durick and seven other colleagues wrote the letter "A Call For Unity", calling on King and "outsiders" during the Birmingham protests of 1963 to stop and let the courts work toward integration. King responded with his "Letter from Birmingham Jail", voicing disappointment in the white clergy, who should be "among our strongest allies". This, and the message he got from Vatican II, led Durick to become a strong voice for civil rights in the segregated South, for which he was called a heretic and a communist by his tradition-bound congregation. In 1968–69 especially, he faced serious opposition in the form of boycotts of his public appearances.