"Nonsensical" seems a bit strong. The article describes language's real "rules" as conventional, coming from usage, and labels more pedantic approaches to rules as stylistics. That seems to me to be pretty accurate. The description doesn't approach registers of speech, and we do need to consider those. But there are lots of "grammar rules" that are really just elements of style best ignored and which are often misused. Some examples: don't end a sentence with a preposition, don't split an infinitive, "passive voice." That last one is a hoot because most of the people who complain about its use can't define it accurately and fail to recognize that it is often valuable. It's also a good example of how there are better ways to approach this sort of thing than applying these particular rules. People commonly attack the "passive voice" because it confuses the actor. So it's much better to talk to people about making agency clear in a sentence, or about why one might be trying to obscure agency. Anyway, that's all my two cents. (I am an English professor, and I've taught for almost 25 years, but I am not a linguist nor a composition expert. So, I'm offering an informed but not quite expert opinion.)