In Colombia, in 1948, a coup crushed the challenge made to the traditional political order by the progressive liberal Jorge Eliécer Gaitán. Among those who paid the highest price for the season of violence and instability that lasted until 1958 were the many Protestants in the country, on whom the accusation of conspiring with the old liberal party and foreign democracies fell without distinction. Colombian Catholicism had a role in providing religious justification for the government's persecution. In fact, the Catholic episcopate was convinced that Protestant proselytism, which was stronger and more widespread than elsewhere, represented a threat to the revival of Catholicism after a long period of marginalization and conflict with the political powers during the years of liberalism (1930-1946). This paper focuses on the fierce defamation campaign against foreign missionaries launched especially by Jesuits during the so-called decade of La Violencia.