Excuses for Repression

But how could the ruling classes whose members were devout Mass-going Catholics justify such brutal opposition to the work of their fellow-religionists?

Well, "certain elements" were adopting Marxism. Foreign missionaries, especially nuns, had "subversive intentions". Their activities were "Communist-inspired". So: in the interests of the State, of national security, internal stability, law and order ...

Turning from the general to the particular, how did all this affect El Salvador?

It has all the statistics to qualify as a Third World country: a capitalist economy dominated by the "Fourteen Families"; 57.5% of land owned by 1.9% of population; 91.4% owned by 22% of population; an illiteracy rate above 40%; full-year employment for only 37% of the people; an urban infantile mortality rate of 85.3%; widespread malnutrition amongst children owing to an export-oriented economy; poor health facilities. (1980 figures, World Council of Churches.)