(Slashdot's Keynesian group think shows through strong in the moderation here.)
Situations where the tax loss is smaller than the cost saving are rares. Most of the time, austerity just kills the economy without any benefit.
I challenge your assersion of that claim.
Additionally I submit that government spending causes the players in the economy to act in a way that benefits them the most in receiving that government spending while supressing their drive to be purely efficient and productive. In the end, we end up with a bunch of players chasing the freebies from the government just because they're free rather than being productive and sustainable.
But you probably won't believe this until this spending kills the host, as the GGP post called it.
I don't know about groupthink, unless you call empirical evidence "groupthink". Herbert Hoover's response to the great depression, Europe's current austerity programs, Japan's "lost decade", Kansas' economic explosion under Brownback: all of these are evidence - from multiple cultures, time periods and scales - that your theory doesn't work in real life.
Let me guess: Your response will be a variant of the "No True Scotsman" fallacy...