That 'LOL' comes across as very arrogant for someone who seems to have a tentative grasp at best on what they're commenting on. We have already experienced stagflation which runs counter to a lot of Keynesian ideas about inflation. It turns out it doesn't always encourage spending and employment. Similarly there is no evidence deflation will lead to stagnation of productivity[1]. People will always want to spend more than is needed for survival and doing so in a deflationary environment makes people think harder on how money is spent.

[1] Read this for a more comprehensive view of deflation from an economist who lived through it: https://www.amazon.com/Economic-Changes-Production-Distribut...