Yeah the article is meant to confuse and sell.
That being said, the other side uses the very same strategy. A lot of abstract terms are not defined clearly: Terms like "strong" versus "weak". Or idea that it takes "a lot" of work to beat the market. What does "a lot" mean? Isn't it more interesting to try to understand what it means to "be" in the market, and what it actually mean to "beat" the market?
If someone approaches you and asks for your money, and also asks to charge fees for holding that money, in return for a promise to be "active" with that money, tell them to go active themselves. Unless they are wiling to explain every single buy, sell, and hold decisions, and you understand, agree, and believe in their strategy, you should not bother.
The other side, the sellers of index funds, are not borderline malicious as the active people are, but I do believe that they are confused by what it is they are offering. The whole theory of efficient markets does not work, because it is impossible to value most companies. It should not matter that millions of people vote for a company with their money, if it is impossible to obtain an answer then that is just the way things are. The whole world has been wrong before many times.
What the index fund bet really is is this: The total market value of the S&P-500 today, to use as an example, is approximately 14 trillion. This value represents the combination of human ingenuity, work and use of capital. The 14 trillion is some part of all the money in the world, let's say X percent. Your bet then is that in 5, 10 or 20 years that value will be a greater portion of all the money in the world. You are in fact betting that we humans, using our ingenuity and capital can continue to create value and better our lives. This is good bet to have. And, this is the best bet to have if you don't want to take the time to analyse individual companies. You only choice then is if you want to bet on the whole world, the whole industrial world, all the Americans, all the Canadians, all the Europeans, etc, etc.