I think you are laying out the argument wrong.
Keynesianism isn't about the role of money. It's about the role of the individual vs the role of some top-down authority structure.
And the way to annihilate that argument is this:
Austrian Theory distributes the weight of the economy across the entire economy itself - across all of the participants. And when each participant adds his preference to the pot, the result is balance.
Like our bodies. The maintenance of our bodies is distributed across trillions of individual cells each adding their needs to the whole.
Top-down theory is unnatural, results in INEQUALITY, INEFFICIENCY, and tends toward CORRUPTION. It's as simple as this: Would you rather have a KING or a DEMOCRACY ? (I know a democracy allows for the possibility of a majority to out-vote a minority. no analogy is perfect)
Have you ever heard of the WAZE App for iphone or android ? Each driver adds his Point of View to the entire map and the result is a well-functioning "organism" (program) (economy)