I didn’t hear him so I have no idea how he responded but evidently he wasn’t exactly truthful about the ban on issue ads in the bill:

At 11:45, he says “they added on something that was a mistake — and that is the issue ad that you were talking about, and I voted for all of it. So I support the first part [the ban on soft money to parties], but I don’t support that.”
Fact: He did support it. You can debate about what you support when you vote for a bill on final passage that has warts, but when you sponsor a bill, it’s your work. No one makes you sponsor your own bill.
[…]

But the original bill still prevented groups like the NRA, NTU and the Sierra Club from running ads to lobby Congress or candidates without going through a ridiculous set of hoops to do it.

Fred, yes it was a mistake. But it was your mistake. Admit you were wrong. Call for repeal of this provision that tramples on the First Amendment.

[…]

Thompson filed an amicus brief (pdf., see pp. 26-30) to the Supreme Court defending not only the original language banning groups from running issue ads, but the toxic Wellstone amendment too!

So he sponsored it, voted for it, and then defended it in Court.

I agree that Thompson should either admit that he blew it and made a mistake supporting the bill or admit that he believes political speech should be limited. He needs to come clean. I don’t think we really need another politician in this race telling us what we want to hear or avoiding owning their mistakes. We have enough of those in the race now as it is.
Update: Here’s the audio.