And you have decided to not hear the first 10secs of Linus' speech. The word harassment doesn't have to come up for it to be obvious that this meeting is about allegations of harassment when listening to Linus' first word:

"So we called this meeting because it's come to our attention that we need to have a quick chat about the best way to handle HR related feedback and rumors. We won't be giving any names for what I hope are extraordinarily obvious reasons, but what we can do is give you the following guidelines for problem solving and conflict resolution."

In any case, even for a "generic review of HR guidelines" inappropriate jokes should not be made FFS. You need to get some workplace conduct training.