I think a situation like this is better handled one on one--wait for a natural break, pull the interview lead aside and explain politely that you appreciate the time and consideration but think it is just not a good fit culturally. Then the lead can explain it to everyone else and excuse them from the rest of the interview process.

Announcing any kind of surprise or unwelcome news can be problematic in a group situation. When people have an emotional response, they want to express it, and in a group situation the mutual reinforcement can quickly scale up the emotion.

This is why it's generally not a good idea to quit by standing up in a staff meeting and announcing it to everyone at once (unless you're trying to make a scene :-)). It's much smoother to tell your boss first, so that they can help manage the emotion of the team.