They Were ALL Universally Mortified...
Because they were all subject to an inherently mortifying action, being made the butt of a joke in front of a large group of people. Same reason that children are universally mortified when their names come up in the bullying circle at the playground.
And I don't believe that the cast the roles of People Sitting Behind Charlize and Naomi, finding the best Mortified-Lookers among improvisational actors.
I think I depart from you on two points:
1. Whether the supposed sins of the actresses deserves this treatment. I don't get that Nudity In Films is now high on our lists of political priorities.
2. Whether a Host-- and a Host invites his Guests -- should call out his Guests in such an embarrassing manner. I do not believe these women were "in on it" (and neither were the people behind them), I do not believe they were given a heads up. And I think the joke is not funny, or even notable (this wouldn't be funny on Family Guy), except for the "Oh My God, he's doing this right to their faces, in front of everybody" factor.
I know MacFarlane didn't personally invite the women but his producers (in on it) did.
Mockery is fine. But I consider this mean, and low, and dishonest (no one gave them a heads up and gave them the power to decide if they wanted to be present for this), and I don't see how it can be justified except on a "Get Our Enemies" level.
I don't even really understand how they would be our enemies, either. I don't really know anything about them, except that they make a lot of movies I don't watch.
I don't think if the shoe were on the other foot -- if someone we liked were put in a position of being mocked in front of the playground for a dubious "sin" -- we'd bless it. I think it fails the shoe on the other foot test, so I can't bless it just for the Dreaded Other.
It would be one thing if the people involved had posed for, say, Playboy. Everyone understands that's for prurient interest, and money, and the ego-stroke factor. But I see these actresses as doing their jobs, and one unpleasant aspect of their jobs is that they will sometimes be required to do nude scenes they'd rather not do, but then, they do need to work, don't they?