The Peril of Knowledge is Pride
It might seem a very strange thing for a Christian pastor to warn against knowledge, but in a society that worships knowledge (and its mother education) the warning must be given.
The central peril of knowledge is pride: "Pride puffeth up". The guy with a degree in history will not listen to someone without a degree in history talk about the second world war: he despises him. The woman with a degree in physics can't stand listening to a biologist rattle on about the second-law: she despises him. You really have to experience it to believe the levels of pride that plague the academy and those trained within her walls.
In the church pride continues to be a plague. The pastor with degrees in what-not or the bible-college trained Christian too easily despises his fellow Christian sharing some deep mystery of the faith because they're amateurs.
Of course this worldly foolish one-up-manship is just plain absurd. It is very likely that an outsider with the ability to think 'outside the box' will have insights that are simply impossible to the insider because the insider is blinded by prejudice or paradigm. Remember all education imposes blindness and sight in about equal measure. There is no good reason whatsoever why a chemist couldn't write a far more interesting - and accurate - book on the second world war than any historian trained in his sacred art.
Knowledge in the church
The grave danger of knowlegde in the church, in addition to pride, is three-fold. I am thinking here of the pure and naked quest to know stuff, whether Scripture, doctrine or church history.
First, it creates an hierarchy or priesthood, between those who know and those who don't. Imagine the home-group where someone knows but the rest don't. Instead of all one in Christ, you have a priesthood of insiders and then the outsiders. In point of fact we all have the Spirit who teaches us (1 John 2:27) and Paul says to the Christians he writes his most sophisticated Gospel to, that they were already "complete in knowledge" (Romans 15:14).
Second, the impression that we must know A, B and C, prevents people from becoming disciples. If the impression is given that knowing stuff is what counts, those who don't know will be discouraged from the start. When in fact what does matter is growing to know Christ better day by day, learning to love him and obey him and learning to love my fellow man. Not attaining some academic knowledge which I could spew out in a test, but personal knowledge of Christ which is often forged in the mines of suffering, not the classrooms of any academy.
Third, knowledge, I return to the peril, used unwisely is just plain dangerous. There is a saying among brethren circles that goes something like this: "Doctrine in the hand of a fool is like a sword in the hand of a drunk." Someone who knows stuff but does not have the wisdom to know how to use it will be a catastrophe to everyone around them, cutting them up and destroying them.
Unless our knowledge is used in humility and with the purpose of building one another up - and it takes time to learn how to wield the sword of truth wisely - it's not only in vain it is perilous.
What does love-with-knowledge look like? Often it looks like silence: you do not have to correct every wrong saying, comment, statement. Sometimes it looks like a one-to-one chat: an open correction rarely accomplishes any good. It may result in a blog which warns against the peril of knowledge not clothed in edification or love.
Or a quote from an ancient warning about knowledge without experience:
"Of what use is it to discourse learnedly on the Trinity, if you lack humility and therefore displease the Trinity?... I would rather feel contrition than be able to define it. If you knew the whole Bible off by heart, and all the teachings of the philosophers, how would this help you without the grace and love of God?" (Thomas A Kempis, The Imitation of Christ, chapter 1)
I know what I am talking about. As a young man I spent a few years growing in knowledge without growing in grace and as a result I was a walking disaster wherever I went. (Of course back then I thought I was a walking apostle.) What that now-bitter experience has taught me is an awareness of the peril of knowledge without love or humility in the church of Jesus Christ which so often plagues the western church.
"Like a thorn bush in a drunkard's hand is a proverb in the mouth of a fool." (Proverbs 26:9)