Excellent point. Martin Luther added some excellent perspective to Christianity. So did C.S. Lewis. Neither claimed to be the second coming of Jesus Christ.
So why do Protestants treat his un-Scriptural teaching of "the Bible alone" as infallible?
Catholics follow the teachings of the Bible that was written, preserved and canonized by Christ's Church.
"If they still refuse to listen, tell it to the church; and if they refuse to listen even to the church, treat them as you would a pagan or a tax collector." --Jesus"if I am delayed, you will know how people ought to conduct themselves in God's household, which is the church of the living God, the pillar and foundation of the truth." --St. Paul