Is Bernie Sanders Responsible For Gerald Friedman's Economic Analysis?

I've gotten enough tweets like this that I suppose I should probably respond:

The topic is Gerald Friedman's paper suggesting that Sanders' domestic spending program will supercharge the economy in wildly unlikely ways. And it's true that Friedman isn't officially part of the Sanders campaign team. But they've previously relied on his analysis of their universal health care plan, and the campaign's policy director has repeatedly praised Friedman's paper:

CNN: "Sanders' policy director, Warren Gunnels, also defended the estimates, noting the candidate is thinking big. 'We haven't had such an ambitious agenda to rebuild the middle class since Presidents Roosevelt, Truman and Johnson,' he said."

Pittsburgh Post-Gazette: Warren Gunnels, policy director for the Sanders campaign, hailed the report’s finding that the proposals are feasible...'It’s gotten a little bit of attention, but not nearly as much as we would like,' Mr. Gunnels said....'It’s a very bold plan, and we want to get this out there.'"

NPR: "As for whether he was worried about these sorts of criticisms hurting the campaign in the future, he said no. 'That does not bother us at all,' he said. 'What bothers us is the fact that the U.S. has more kids living in poverty than nearly any major country on Earth.'"

Come on, folks. If your policy director is out in the media promoting Friedman's paper, then it means the campaign is standing behind it. There's no two ways about this.

The second line of defense for Sanders' supporters is that no one has proven that Friedman is wrong. In fact, the critics are "the establishment of the establishment": just a bunch of Wall Street shills on Hillary's payroll who have it in for Bernie. I'm at a loss about how to respond to this. Obviously you can't prove that a forecast of the future is wrong. But you can say that Friedman is forecasting a sustained level of economic growth that's literally never happened before in history. Not here, not in Denmark, not anywhere. Mature economies simply don't grow 5 percent a year for a decade. Labor productivity doesn't double just because you create a bunch of social welfare programs. The number of people in the labor force doesn't skyrocket to new records even in the face of increasing rates of boomer retirement.

The discouraging thing here is that Friedman's critics aren't saying that Sanders' proposals are bad. You can support every single element of his plan with a clear conscience. Their criticism is solely about forecasting how his plan will affect economic growth. And on that score, it's not even remotely realistic. It's about like saying his Medicare-for-all plan will increase life expectancy ten years. It's beyond belief. No matter who you support, you shouldn't do it based on fantasies like this.