Truthfully, I don't believe the left believes that soaking the rich is an economic winner. Their desire to soak the rich is "justice." It's just not right that they have that much. Really, it's not even about redistribution. Yes, it allows entitlement programs to continue, but really it's simply about taking it from the rich, because in their mind it was never their money in the first place. Allowing them to keep their own money is really the government giving them money in the liberal mind.
But Schiff is right; to defend this theft the left has tried to argue that it's also good for the economy. This is, of course, absurd, but many still believe it. And in case you've forgotten, who cut the 91% rate to 70%?