Christ's Revelation to John is understandable through faith in Christ.
Without faith in Him, the understanding isn't made available by God the Holy Spirit. Without the ministry of God the Holy Spirit, the book isn't as easily understood because it communicates many spiritual things beyond the perception of the senses or the mind. Faith is a system of perception which is preceded by acceptance of God. He does all the work in His grace.
Hmmm...I certainly understand enough of what I read in the Bible to where I don't go around judging and questioning the faith of others based on one remark. ;-)