Given the amount of uncertainty central banks create with arbitrary changes to monetary policy (or non-changes under Greenspan), cooperating/competing with other central banks, differing objectives, etc., and all the politics involved in stimulus, TARP and our current situation, do macro-economists get macro-economics? And is that supposed understanding used by politicians for their own gain?

I'm no macro-economist (although I do have an economics degree), but I believe deflation and inflation are acceptable as long as they are gradual changes and don't enrich or impoverish one segment of the economy over another. I think a lot of people are wary of the Fed (and Congress for that matter) overreacting to current economic conditions in order to stabilize prices AND maximize employment, messing up one or the other in the process, as Greenspan & the GSA-induced malinvestment in housing did.

The curious task of economics is to demonstrate to men how little they really know about what they imagine they can design.

-F.A. Hayek, The Fatal Conceit