From the linked transcript:
BLUMBERG: But fortunately, as you know, plank three I think is something that people can get around - a massive tax cut.
SMITH: OK.
BLUMBERG: Are you ready?
SMITH: Yeah.
BLUMBERG: A tax cut that's an insidious tax. It's felt everywhere in the American economy. It destroys jobs, stops innovation.
SMITH: I am all for it. OK. Who gets this tax cut?
BLUMBERG: Not who - what.
BAKER: If I'm being blue sky here, I would say the corporate tax is totally a waste.
FRANK: The corporate income tax makes no sense whatsoever.
SMITH: You are killing the voters here. So far we've got raised taxes on the middle class and eliminate taxes on corporations?
BLUMBERG: Yeah. And those were the two most liberal members of our panel, Dean Baker and Robert Frank. And here's the reason that they and pretty much all our panelists hate the corporate income tax, which by the way is one of the highest in the world here in the United States at 35 percent.
BAKER: It doesn't make sense really to tax the corporation as such. What we want to do is - I'm going to sound like a Mitt Romney here. What we care about is if the corporation is reinvesting the money. What's wrong with that? Why do we want them to prevent - why do we want to prevent the corporation from reinvesting the money?
What we might want to prevent is giving the money to wealthy shareholders or them buying a second, a third, fourth home, getting a new Mercedes every six months, whatever it might be. That's where we want to have the taxes. We don't want to prevent Microsoft or General Motors or whoever it might be from investing more in improving their product line. That's a good thing in my view.
BLUMBERG: So a lot of people, you know, when they think the corporate tax, they want to keep the corporate tax in place because they want rich people to pay more taxes.
SMITH: And rich people own corporations.
BLUMBERG: Right. But our panel agreed. If you want to tax rich people - and not all of our panelists agreed, by the way, that you should tax rich people more than others - but if you did, if that's what you wanted to do, just tax rich people - do that. Don't tax the corporation.
tldr: Taxing corporations prevents them from reinvesting the money and doing such things as advancing technology and hiring workers. It is a terribly destructive tax, discouraging exactly the sort of activity that drives the economy. It's the people who own the corporation that you're trying to tax, so tax them when they get the money.