Pope Gregory ought to have been ashamed of himself for alleging, for his own autocratic purposes, that the Holy Apostles were guilty of such behavior!
The reference given in the encyclical is to Acts Chapter 19. Here St. Luke tells us that some pagans who had practiced sorcery repented of it, and burned their scrolls as a witness when they converted to Christ. Nowhere does he claim that the Apostles burned any books, and certainly not any books that belonged to others.
In fact, St. Paul (the Apostle involved in Acts 19) made it very clear in 1 Corinthians 5:12-13 that it was not his business to judge those outside the Church.
Oh good heavens! You mean that some people actually had this silly notion that it was an abuse of power to suppress ideas with the force of arms, and that bad words could be overcome by good ones? Clearly they must be stopped!
Nor can We predict happier times for religion and government from the plans of those who desire vehemently to separate the Church from the state, and to break the mutual concord between temporal authority and the priesthood. It is certain that that concord which always was favorable and beneficial for the sacred and the civil order is feared by the shameless lovers of liberty.
Or, one might get the impression that those who call for censorship are afraid that their own views might not hold up very well when exposed to criticism; and that those who wish to yoke themselves to the world by having the State sponsor the Church lack confidence in Christ's promise that the gates of hell will not prevail against her.
Anyway, thanks for the new tagline, Gregory.
18 And many of them that believed, came confessing and declaring their deeds. 19 And many of them who had followed curious arts, brought together their books, and burnt them before all; and counting the price of them, they found the money to be fifty thousand pieces of silver. 20 So mightily grew the word of God, and was confirmed. (Acts 19)
Pope Leo XIII says
the apostles themselves burned a large number of books
It is true that the burning of the books was voluntary. However, are you prepared to say that the apostles had nothing to do with the burning? It is by their witness that the sorcerers renounced their craft (Acts 19:15). The account of the book burning reads like a story or triumph -- not of oppression, but of conversion.