It's one of the more informed technology websites.
It's easily possible they don't know what GNU is beyond "the tools used with
Linux". Have you emailed them? They may be interested. For instance, in this
article
(https://www.theguardian.com/technology/askjack/2016/jan/07/when-and-how-should-i-upgrade-my-old-windows-vista-laptop)
they actually not only mentioned something other than Windows, but GNU too. I
was pretty surprised... so it is more a matter of people not knowing to
acknowledge GNU than stubbornness.
Also, ignore the troll comments on Ars. The people on it are usually
well-informed and polite (and humorous).
If the Ars editorial staff really don't care then just keep commenting on the
articles. Some people might be more inclined to listen.
