That question was posed by the author of a Bible study we were working through in Sunday school. The passage of Scripture we were working through was found in John 8, and involves the crowd trying to trap Him with the case of the woman caught in adultery.
I know the author is trying to get us to think through the incident, but the question is quite ridiculous and only has one answer: We would have acted just like everyone else acted on that day.
I guess some people might think they would actually be wise enough not to get caught up in the crowd, because… they know what Jesus is going to do before He does it. In other words, those who think such thoughts are thinking they would be partially omniscient in that situation. (Partially omniscient is an oxymoron).
The point is, why ask the question? We cannot be there? We cannot even come close to imagining what it is like? And there is only one correct answer: we would have acted the same as everyone else. I guess that has some value in helping us to see that we are no better than those who lived in Christ’s day. But do we really need that type of question to bring out that truth?