It was an insult; anyone would have since you gave no regard whatsoever to the person's opinion. Simply dismissing it and then saying the person is pitiful is outright rude and immature. If someone did that in my classroom, they'd be sent right to the Principle's Office, no rebuttals.
Why is it fluffy?
1. It is chuck-full of a warm, fuzzy-wuzzy feeling that Jesus is simply your best buddy. That's a strange, new doctrine begun in the 1960's with the Jesus Movement. Jesus is not our best buddy but our Messiah and Savior and, with God the Father and God the Holy Spirit, our Divine Parent. He wants a close relationship, yes, but in a Father-Son type, not a "yo dude!" sort.
2. It neglects to give any sort of actual history of Christianity. Why is this important? Because I cannot count anymore how many Christians are ignorant of their religion's past (and yes, I said religion). If you went to a person who owns that book, even if he or she is a firm church-goer, and ask him or her, "what is an Ecumenical Council?" or "is apollinarianism a heresy?", 99 out of 100 times, you'd get a blank stare. Christianity has 2000 years of doctrine, Councils, and history to it. Just because a person accepts Jesus as their Savior doesn't mean that they can now follow heresies and reject the rest of their new faith!