Antonious Nikolas said:
and by detractors as Christianity perverted by Marxism and Communism”
It is not "by detractors" but by the very heads and "fathers" of the movement. See this article from the Brazilian RC site "Montfort":
The ex-friar Boff gave the following declaration in an article for the newspaper Jornal do Brasil, April 6th, 1980:
"What we propose is not theology inside Marxism, but Marxism (historical materialism) inside theology".
And more: "The method of the Liberation Theology...is the dialectic method." (Leonardo e Clodovis Boff, Teologia da Libertação no Debate Atual, Vozes, Petrópolis, p. 22).
"Liberation theology starts up from this kind of interpretation of reality: social, radical and dialectic criticism, structuralist." (L. e Clodovis Boff, Da Libertação, Vozes, Petrópolis, 4a edição , p,17).
Boff explains the consequences of all this: "In Liberation Theory, the fundamental issue is not theology, but liberation" (L. Boff e Clodovis Boff , Teologia da Libertação no Debate Atual, Vozes, Petrópolis, 1985, p.17).
This pseudotheology proposes liberation from what?
"When I speak of liberation I positevely understand this: to end the system of injustice that is capitalism. It is to liberate oneself from capitalism to create in its place a new society, let's say, a socialist society." (Leonardo e Clodovis Boff, Da Libertação, Vozes, Petrópolis, 4a edição , p, 70).
And more: "It is necessary to say clearly and boldly: liberation is the emancipation of the socially oppressed. It is positevely for us to overcome the capitalist system in direction of a new society of the socialist kind" (L e C. Boff, Da Libertação, p. 113).
"If I so express myself it is because, for us, today, the Kingdom of God is positively socialism" (L. Boff e Cl. Boff. Da Libertação, p. 96).
"The therapy presented by this radical critical conscience is not the reform of the (capitalist) system; this would be to treat the symptom without noticing the source producing the disease; we propose a new way of organizing all society over new different fundaments; no more over having capital on the hands of few, but from the work of all, with the participation of all in the means of production and in the means of power; we speak of liberation" (L e Cl. Boff, Da Libertação, pp.16-17.)"
http://www.montfort.org.br/index.php?secao=cartas&subsecao=politica&artigo=20040729135508&lang=bra
So no, that Liberation Theology is the attempt to innoculate Marxism in Christianity is not a theory of detractors, but the declared aim of its authors.