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I wouldn't necessarily call what you have there a "critique of Keynes' policy". It's more just a soft argument against banker intervention.
I'm not quite sure what you mean by bankers "acting frivolously", and leading to "raises prices higher that the economy actually has in cash"...and I'm also not sure where you got the number "sometimes 10 times as much". I believe there's roughly somewhere around $3 trillion in actual US cash. We have a $14 trillion GDP. In 2007 the value of the OTC derivatives market was around $595 trillion. (Yes you read that right. Almost $600 Trillion. For some perspective, the annual GDP of planet Earth is less than $60 trillion.)
I'm also not sure what you mean by prices rising higher than the amount of cash "ecause the investment and high-street banks know that the central banks will bail them out".
You might check out that link above and see if you can find some specific resources to help get you some more details on what exactly you're trying to say.
