lol @ CC replacing letters with asterisks for a Japanese word
Are you passionate about it? Is it something you've worked on or read a lot about? The IV essay is probably the most important of the shorter essays, since Stanford emphasizes that quality in its literature and the IV essay question hasn't changed for at least 15 years. As such, you should definitely reserve it for something that's important to you. They always say you need to show "passion," and while that quality should be present throughout the entire application, it's especially important for that essay. I don't think that the incident is very controversial anyway in the context of an essay. So it's not the possible controversial nature of the incident that would make me wary of it, but rather that it's not really what you're passionate about - as you say, you've had discussions, but have you delved into the issue much more? If I'm wrong, then by all means talk about it, but do make sure that it's explored in a way that displays your intellectual vitality.
Search the forums; the IV essay is probably the most discussed topic on essays.