This is an attempt by a Brazilian Lutheran theologian to square Luther's teachings with Liberation Theology. Luther's ideas set in motion a new era of human emancipation. But the man himself wasn't an egalitarian by any means. The Catholic Church had to go, but temporal authority was put there by God. Thus Luther's exhortation to the Princes to slaughter the revolting peasants as if they were mad dogs.
At their most radical, Luther's ideas brought the notion that we are all equal before God down to earth. Equality was no longer a spiritual abstraction, it was a living thing. All are part of the universal priesthood and therefore all work is equal in its importance: both the ditchdigger and the doctor have something to contribute. From this follows the ideal of universal literacy. Everyone should read the Bible.
But when faced with the revolutionary consequences of his ideas, Luther retreated into a "free your mind instead" kind of guy. When all work is equally important, there's nothing wrong with being a serf!