The author is a known critic of the demonetization policy. This was a complicated decision and it is still unclear whether it worked or not. I personally know a lot of business owners and merchants who really hate Modi for this move - which I feel is a good sign given these are the very people who kept the so called black money hidden from the govt and were negatively affected. Of course, the GDP would fall given economic activity got affected at the grass roots level.

That said, there were some benefits 1) people would think twice before hoarding onto cash and keep it hidden from the govt 2) more people would use banking facilities as the govt basically forced a lot of people to create bank accounts and deposit cash there for easy tracking. Also, there are long term tax benefits for the govt too given now it has a snapshot of who exchanged how much black money (in old notes) with the new notes. As such, the answer isn't black or white here.