The point of view underlying von Mises’s—and von Hayek, and Marx, and Ron Paul—complaint against fiat money in general and monetary management of the business cycle in particular is this: that value comes from human sweat and toil, not from being clever. Thus it is fine for money to have value if it is 100% backed by gold dug from the earth by sweat and machines and muscles (even if there is no state of the possible future world in which people actually want to exchange their pieces of paper for the gold that supposedly backs it). But it is not fine for money to have value simply because it is useful for buying things.
Another Note on Von Mises’s (and Ron Paul’s) Monetary Mental Disorder
Brad De Long has been spending a lot of time on Mises and Austrian economics. Some really interesting reading.