Walsh was raised a Roman Catholic and throughout his life identified himself as a Catholic and practiced his religion both in public and in private. An altar boy as a youth, in his adult years he regularly attended retreats and participated in meetings of Catholic laymen. Senate colleagues recognized his Catholic faith and occasionally baited him by challenging him to defend himself as a partisan of Catholic interests, which Walsh did not hesitate to answer. Once when a senator accused the Catholic Church of attempting to involve the United States in the Church's battle with the government of Mexico, Walsh defended the Church at length, saying in part: