This is crazy. I've seen it done plenty of times by accident in the past, because people don't know how to use BCC (and its hidden by default in many clients).
Nothing I've heard about this case sounds to me like an innocent mistake that a reasonable effort was made to correct.
I've accidentally smacked people on the street before (gesturing, probably). That's technically a crime, but it'd be crazy to prosecute me for a little mistake like that. But it's not crazy that hitting people is a crime and that people do get prosecuted for it in egregious cases.