According to Wikipedia:
Revelation was among the last books accepted into the Christian biblical canon, and to the present day some churches that derive from the Church of the East reject it.[18][19] Eastern Christians became skeptical of the book as doubts concerning its authorship and unusual style[20] were reinforced by aversion to its acceptance by Montanists and other groups considered to be heretical.[21] This distrust of the Book of Revelation persisted in the East through the 15th century.[22]
Dionysius (248 AD), bishop of Alexandria and disciple of Origen, wrote that the Book of Revelation could have been written by Cerinthus although he himself did not adopt the view that Cerinthus was the writer. He regarded the Apocalypse as the work of an inspired man but not of an Apostle (Eusebius, Church History VII.25).
We can see that there were already doubts about the authenticity of the writings just a few years after the death of Jesus and during the time the various books of the Bible were being compiled. Obviously brother Eli has faith in all of the Bible writings, so whatever is included in the Bible is what he firmly believes in. However, with such early controversy, can we ever be sure of what we believe without actual proof?
If we can't even determine WHO actually did the writing, how can we trust the nature of the person doing the writing? That person could have evil motives and we would never know it.