Originally Posted by Ronaldinho
This doesn't mean agree with everything he says. But if he says something you have a visceral reaction against, things like, "That's interesting. I'd have to think about ways to make it work," or "I like that idea but it presents some challenges like X, Y, and Z" are responses that keep the conversation going and make the producer feel like you're working with him.
My strategy if I get a note that really freaks me out is to say, "Hm. So you're saying..." and then summarize the note back to them. It buys you some time to formulate a nice, polite response like the ones Ronaldinho mentioned. (And sometimes I misunderstood the note, so that's always good to clear up quickly.)