I seriously doubt that someone would knowingly cause a crash, or assume that a hotdog move would be accepted in a club ride setting with strangers. Some people are just unaware that they caused the crash.
Ask him if he knows what/who caused it. If he's oblivious, AND is he's going to ride with the group again, then you MUST point it out to him. Be as objective as possible. But otherwise, move on. Kicking his butt will only create a more dangerous situation.
One more comment: if you had seen him riding in a manner that had crash-potential, you could have pointed it out to him pre-crash in a very diplomatic and nurturing tone so as not to offend anyone.
Or were you going too fast?