I do the same (when I remember to, that is), though in this case, I was actually referring to the fact that "gnostic" and "gnosticism" are only capitalised when referring to particular sects of Christianity, rather like how "communism" is only capitalised when referring to a proper Marxist regime, not the over-arching belief in the abolition of private property.
BTW, if you read the article all the way to the end, you might notice something a little strange. In the English translation of "We," the word "reason" is capitalised for a similar reason. The full sentence is "Потому что разум должен победить," which means "Because Reason must prevail." If you've never read "We," you should.
I haven't yet had time to listen to the entire presentation you linked in that article, but it is an intriguing argument. He's one of the guys behind the fake gender studies article prank/scandal, right?
Close: Alan Sokal was the one behind the fake gender studies prank, James Lindsay and Peter Boghossian were the ones behind the fake race papers.