I'll take the word of a Paul Johnson, even if he were to argue the earth is flat, over the gibberish from some anonymous poster on an obscure Internet forum, who doesn't know the difference between "its" and "it's", and claims his life's mission is to "defend science"!
I don't know if I'd take Paul Johnson's word for it, but I'd certainly pay attention.
But I have to defend people who get "its" and "it's" confused, as its a mistake I often make and have the hardest time catching.