This exchange reminds me of how men are often told to have "open and honest communication", but then when a guy says what he really and honestly thinks, it gets turned around as being "cold and harsh".
Pete commented on a hypothetical situation, and he stated his point of view. Not to be mean, or hurtful, or disrepsectful. At worst, it could be considered insensitive, but you invited him to share his opinion by opening the question.
He shouldn't have to feel guilty for that.
You can talk to him about how this topic hurts you because of the feelings it stirs up, but I think in no way should you make him feel guilty for expressing his thoughts in a hypothetical situation.