The ad hominem attack is not helpful. However the reasoning that may have led to it may still be valid. The author fails to meet the prima facie burden of his argument. He presents some evidence, but does not connect it up to a solid argument. For example: Instead of explaining why the "I believe" is not an assertion of an opinion but a hedging of a bet on a fact, he just leaves the kid confused. I don't see the connection from "these are facts while these are opinions" to "cheat on your tests! Pave the Earth! Vote for evil!" If I'm missing it, please help me see it. Otherwise it's just some slippery slope stuff.
Thanks for reading past sentence one before writing me off. I don't have any remote problem with anyone who holds the moral facts stance. I personally don't agree with it, but I won't insult someone simply for having different thoughts than me. However, it does irritate me when writers for high profile publications post awful arguments, and everyone hails them as a genius without stopping to think 'Maybe this person isn't infallible.' It's frustrating to watch people lose their critical thinking abilities when they read something that looks official.