The argument against helicopter money as a means of boosting aggregate demand is it is inflationary.
Not necessarily if the velocity of money increases and there is an output gap.
A thought experiment though imagine there was no guarantee of this.
Monetary financing would deflate the value of a currency against other currencies and increase input prices – leading to at least short run cost plus inflation.
But what if every currency did this?
If there was an even balance of trade between each country there would eb no inflation – the effects would cancel. This is I think the thinking behind Hawtrys monetary parable of ships racing to port in a storm – the argument being if you are in a storm you get there as quickly as possible.
Decisions, Decisions, Decisions 
With the dual policies of a universal dividend and a retail discount to prices that was gifted back to participating merchants the national problem of any inflation would be completely and ongoingly resolved. Furthermore, every producer in the cosmos would be rushing to sell their products/services in an economy which enabled them to sell their products at a 40% discount in an economy of abundant demand….and get every cent of their discounts rebated back to them so…..who would give a shit what any bogus financial agency erroneously thought about it or even down graded their currency trying to prevent it????? Finally, if each nation implemented the same policies dependent only on their present ability to produce…every single one of them would be continually stable and booming.
You and Keen are both sad erudite dunces and way behind the curve when it comes to actually looking at the temporal effects of the integrative policies of Wisdomics/Gracenomics/Social Credit.