are saying that taxing people diverts spending away from non gov't goods and services, you are wrong
No, I'm saying that government spending does that, regardless of whether the revenue comes from taxes, borrowing, or glowing presses. Collectively we make what we make (goods and services), and whatever portion of that GDP is diverted into government hands is just that much less for the people (except for the remarkably tiny percentage of government spending that actually goes to needed infrastructure, perhaps, but that's almost a rounding error in recent budgets).
the economy is in a slump; in that case, gov.t spending is good
Oh, yes, it worked so well for the Greeks, I'm sure it will work just as well for us. It's individual consumer spending that has pulled us out of every recession, and that waits on stability more than anything else. The best thing the government can do in a recession is: change nothing: no new regulations, no obviously-temporary programs. Historically people start spending again once they feel they've adjusted to the "new normal".
your idea that lower taxes = more productivity is just wrong in some, and perhaps most circumstances
Again, spending, not taxes, is what affects efficiency, not productivity. "Broken windows" are great for productivity, but do nothing to actually make things better.