Then you are of Apollos or of Paul, not of Christ. (I Cor. 1:10-17)
Jesus never specified a manner of evangelism. WOTM is one of many. A good one but not the ONLY one.
Actually He did. He commanded us to "make disciples" of all nations, which would demand evangelism in the public sphere. This would mean public preaching, public one-to-one, etc. Jesus also specifically commanded door-to-door evangelism, and what He DEMONSTRATED was primarily open air preaching and teaching.
Moreover, we see a biblical principal of "Law to the proud, grace to the humble" that is present in EVERY witnessing encounter in the Bible. There are many "methods" (presentations), but if does not follow that principle, then it is not following the scripture.
To say that this young man is claiming allegiance to a person over Jesus, simply because he is recognizing a book that teaches a BIBLICAL PRINCIPLE, is ridiculous. I guess if I quote a John Piper book that says "Jesus died for sinners" suddenly that teaching is faulty because I read it in a book? Absurd.