Printing money is definitely helpful. Problem is that its basically a secret tax. When the government creates money, it devalues all the currency in the country, acting like a big flat wealth tax on everyone. This makes it difficult for people to save up for a down payment on their house or their retirement. Also, people will be less willing to loan the government money to service the debt if they know their money will actually devalue, which will push up interest rates. So the best policy is inflation in moderation and debt in moderation, and these are best used in hard times, not all the time.
But the numbers really don't support those theories. Prices aren't going up much at all; we aren't even reaching our modest inflation targets, and Japan can't induce inflation for trying. And interest rates on Treasuries remain very low, even though most people consider our national debt to be huge.
This is what I was referring to initially, when I mentioned that our cost/benefit analyses for govt. deficit spending needed to be rethought. Attributing inflation to deficit spending and higher interest rates to the national debt are basically two more ways of saying the same thing - that the government
is limited in money creation, current theories of inflation are correct (we're just really, really good at walking that spending/inflation tightrope), and any more government spending would be less optimal than what we spend right now.
We have been balancing inflation against unemployment (NAIRU thinking) for decades (at least), on the
unproven assumption that there is some magic level of unemployment below which inflation is triggered. But recently, it has become undeniable that low unemployment and low inflation are not mutually exclusive. Which means for decades, the Fed has been adjusting interest rates with the express purpose of keeping unemployment artificially high in order to keep inflation down. Real suffering, based on flawed economic theories.
So before we go down the "Bernie is going to bankrupt the country" road, I think its important that people first understand (for instance) that the country
cannot go bankrupt, inflation is caused by many factors and not just the cost of labor, the Fed still has control over the overnight rate/base price of money, etc. We should really question the reasoning behind austerity, and the legitimacy of claims that we can't afford these programs.