I already partially addressed that. But the liberal argument against the Bush tax cuts isn't predicated directly on its harming the economy, but rather on the basis of fairness and the indirect impact that the tax cuts have by creating deficits that Republicans want to fix through spending cuts.
Also, shifting the wealth to the top as the Bush borrowed tax cuts do puts money being hoarded at the top and driving up the prices of things they own, making ownership less available to more people and reducing the productivity in the economy, which reduces growth... fewer entrepeneurs, fless money with consumers to buy, etc.
That's why plutocracies with wealth concentrated don't make as much wealth.