Giving either response can be harmful if you are trying to avoid the disapproval of someone who fails at conservation of expected evidence. (This failure could happen even to us rationalists who are aware of the possibility, by simply not thinking about how we would interpret the alternative response we did not observe, especially if our interpretation is influenced by a clever arguer who wants us to disapprove.)
Giving either response can be harmful if you are trying to avoid the disapproval of someone who fails at conservation of expected evidence. (This failure could happen even to us rationalists who are aware of the possibility, by simply not thinking about how we would interpret the alternative response we did not observe, especially if our interpretation is influenced by a clever arguer who wants us to disapprove.)