Sometimes I forget that seemingly normal people often have deep wells of The Crazy hiding inside. And I've been trying to limit my consumption of The Crazy, so...
I waited until said coworker was occupied and spoke directly to the student organizer.
"Hey, I was just browsing the website last night and, gosh, I think the rules must have changed since X last checked them, because..."
Wimpy, but effective. And didn't have to absorb any Crazy. Yet.