Read through the article and aside from the 2 anonymous studies that were mentioned, there's not much science let alone other evidence to backup the author's open opinion on the subject. That said, I do agree though that for sitting for too long can be detrimental for you. That's why you balance between sitting for long periods and standing up and moving around. If the author's words were to be taken word for word, then it's written as if sitting is all people do for all hours of the day. The spinal cord needs rest from time to time. The author transitions into a talk about habits and suddenly, the article becomes a topic that's been discussed to death a million times.
Nowadays, any and every self-proclaimed writer will write about anything to try to make the front page. Tomorrow, it'll be "excessive standing and movement causes arthritis."