I’ve been in a similar situation. I asked the criticizers to please desist as I am friends with the person and their conversation made me very uncomfortable. They desisted. If they had not, then I would no longer have respected or admired them. If you are wondering if I defended the criticized person, no I didn’t, I didn’t think it was appropriate in that situation. The person wasn’t there, so there was no need to “have their back” so to speak. A refusal to participate and a request to stop was enough.