[wpietri]

One can take a stand against the kind of bad behavior without being prejudicial toward the accused.

E.g., the organizer could go to the culprit and say, "As you know, Joe, we take sexual harassment very seriously here. Could you tell me what happened last night at the bar?"

I could imagine a lot of ways it goes from there, but all of them seem compatible with taking a strong stand against jackassery without giving up a strong stand for fairness.