Why a balanced budget amendment is a very bad idea.

Two reasons:

1. It constrains what the government can do, to prevent wild fluctuations in the economic landscape.  If an asset bubble bursts (typically considered part of a natural economic cycle in an unconstrained market), then the federal government will have no choice but to cut spending.  In other words, Republicans would like America to go all in on Hayek, and completely reject Keynes.  And if you followed the two years after the 1929 crash, you'd understand that Hoover's laissez-faire did not improve the economy one bit.  You can't even practice voodoo economics, because for every tax cut you enact, you have to balance it with a spending cut elsewhere...and total GDP ends up either neutral or lower, because of how the trickle-down effect works.
2. It gives Republicans the political room to say, "Hey, we can't do anything to help the economy get out of a recession, because we're constrained".  I'm sure you've heard that one before...they'd rather be constrained by rules than take on actual responsibility and political risk that follows from deviating from a strict dogma.  A veritable bailout for Republicans, on their irresponsibility!  You see, if Republicans were serious about deficit reduction, they would not have eliminated the Paygo (pay as you go) rules when they were in power in both legislative bodies and the White House, and the most certainly wouldn't have kept the full cost of two wars off the books by excluding most of the annual costs from the omnibus spending bills.

And that's why a balanced budget amendment is a very bad idea.