Once upon a time, slavery existed on earth and for a good amount of time. It did so because it was carefully sustained by building a narrative supporting it. Michael Munger of Duke University has a good podcast on Slavery and Racism. He summarizes the narrative justifying slavery as follows
since I (master) owned them (slaves) I have a much better reason to take care of them because they are still going to be valuable to me 5 years from now. Whereas if I rent labor, I don’t care: that guy can die; I’m just going to pay him just enough to induce him to come work for me. I don’t have to provide housing; no health care. Whereas with a slave, if he hurts his leg, I’m going to take care of him.In other words, the narrative was that slaves can't take care of themselves, hence it's better for them to be slaves. They would at least be taken care by their master.
The thing about arguing only in terms of economic benefits is that one can defend anything using it - dowry, disenfranchising illiterates and women and so on. The proclaimed benefits can be easily listed down for anything that has sustained for long. It's easy to fall into the fallacy of "something that's going on without resulting in huge resistance (like riots) has to be good because if it wasn't good, it wouldn't have sustained". One only needs a handful of sycophant economists to come up with a narrative handcrafting the benefits. The benefits will be amplified and costs (suffering) are ignored.
By doing so, the defenders carefully substitute the normative moral reasoning for proclaimed economic benefits. These economic benefits never factor in the non-quantifiable moral issues in the calculation.
The difficult part is that it's easy to build a narrative that persuades people into turning off their normative lens. As Michael Munger confesses in the podcast
If you read letters — and this is something that I found so difficult in a way — and in fact, I have nightmares and when I was working on the paper and looking closely at letters would wake up at night and feel bad about this, because I was developing some sense of sympathy for people who objectively I think are terrible. They are slave owners.If one is not the victim and is removed from the situation, it's not easy to perceive the human suffering. So, it's easy to buy into the narrative of benefits, disregarding the suffering. For instance, consider the narrative: "illiterates and women don't know have a knowledge of the world. Giving them the power to vote will be detrimental to democracy". It appeals to our superficial sense of reasoning. Looked at it superficially, such argument based on benefits looks very convincing. It's the power of narratives that turns off the normative lens.
One, normatively speaking, the whole exercise violates one of the fundamental principles of our society/law that it's not ok to punish innocents, even if it's at the expense of not punishing the wrong-doers. A large number of people who have no role in the black money making are being put to enormous trouble and death in some cases, for the wrong-doings of a few. It's literally a carpet bombing.
Two, demonetization is as beneficial as slavery. Sure, there may be benefits somewhere, but at what cost and suffering? If a drug to a disease results in hair growth on a bald head, it's not the reason to pray for that disease and deliberately spread it.
Three, much of the proclaimed benefits needn't even be true. They are just post-facto justifications. If demonetization is such a transformative and groundbreaking reform, one's to wonder, why no one who's vehemently supporting it now, have argued for it in the past? Some economists, who are part of the current sycophant group, even have written books in the past on Indian economy. Demonetization proposal doesn't even get a cursory mention in those books. All this post-facto justification is nothing but sycophancy, deliberately ignoring the large-scale human suffering. Some even term the human suffering as noise, which is reflective of the nature of justifications.