Maukdaddy says that "it depends on the type of personality you're dealing with," and I think that's very true with regards to immediate-and-public versus later-and-in-private. With many people, an embarrassing confrontation in front of the whole team will cause them to dig deeper, because their pride is on the line. The same person might respond more thoughtfully to a private expression of disapproval.
An advantage of doing it in public is that others can see that it's been done. This could include victims of the oppressive joke who will now see justice previal and might stand a smidge taller, and possible future (or past) 'offendors' who will see that that they should be more professional and not make the same mistake as the other person.
It's appropriate to take someone to task privately, while still making public statements of principles and expectations, even alluding to "the tenor of conversational has been unprofessional a few times recently, and it's not healthy, it's not productive, and it's not acceptable. If you hear something that's not right, talk to the speaker, or your manager, or HR, or the CEO. If someone tells you that you've crossed a line, make an adjustment and let's keep working as a team. ".
