Handling a Defensive Reaction to Feedback in a Design Review

You're presenting a checkout flow in a design review. A senior PM says: "I don't think this checkout flow is going to work." That's the entire comment — no elaboration.

Your first instinct is to immediately explain that you tested it with five users and it performed well, and to defend the decision before the PM finishes their point.

1. Explain why leading with that immediate defense, even though the justification is factually true, is the wrong first move.
2. Write two clarifying questions you could ask instead, aimed at finding out what's really behind the PM's comment.
3. Suppose the PM's real concern turns out to be that the checkout flow doesn't handle a promo-code edge case that matters commercially, not anything about usability. Explain why taking the comment at face value (treating it purely as a usability critique) would have wasted both people's time.