Actually this writer is quite confused. Demand side economics is not the same as Keynesian economics. Demand side economics is the opposite of supply side economics. Demand theory states that if something is being demanded, a supplier will come forward and a mutual price will be agreed on. Supply side econ states that if you produce enough of something, it will eventually be demanded. If supply side worked, garbage and criminals would be in great demand and would be considered valuable. No one is demanding garbage or crime however, so the value is low to negative. All markets worldwide function on demand. If you have no buyers, you won’t sell.
Oh wow, I'll bet the supply siders have never thought of this angle before. Their theory is clearly doomed.
The Heritage Foundation paper linked to early in this article also says the Keynesian theory is based on demand.
That's a unique definition, did you make it up yourself?