And by the way, I think you have a cartoonish view of Keynes. One reason why I lean more towards Keynesianism than other schools is because it acknowledges that there is no such thing as a perfectly rational Homo economicus. Coupled with information asymmetries in markets, this means that a pure market-lead economy will result in sub-optimal global outcomes.
This is obvious with even a moment's thought, and you aren't likely to find an Austrian denying it. The problem is, Keynes didn't have a better solution. And "sub-optimal" is subjective anyway.
I would consider a world wide depression caused by over allocation of money into a few sectors a sub optimal outcome. But maybe if we had more central bank intervention and more of government encouraging lending for homes we would be better off.