Oh, they are actors! They're always acting, so sitting there in the fanciest costumes, playing stars at a gala event elevating and celebrating what their character believes is a very grand enterprise, they laughed on cue, presenting faces that seemed to understand what the joke was, but not to the point where they realize that the man on the stage — he's an actor too — is accusing them of participation in evil. Their character is a bit dumb and obtuse, or so earnest about making this gala night beautiful that she pretends not to know that this man is telling them all — in the nicest possible way, under the circumstances — that this enterprise of theirs is thoroughly infected with racism — not lynch-you-from-a-tree racism, not cross-burning-racism, but we'll-always-hold-you-at-arm's-length racism, "sorority" racism, we-like-you-but-you’re-not-a-Kappa racism.
They had to sit there. They'd gotten the role and they were lucky to have it. The evening was, perhaps, a success. Was it? The spectacle felt so awful to me, especially the faces of the actors laughing. What else could they do? Me, I was sitting at home, so I could just turn it off, which I did, after I found myself, one too many times, talking to the TV, saying things like "Look at them laughing as if these are just the usual jokes and the jokes aren't about them and telling them that they are disgusting" and "They're supposed to be demonstrating to us how wonderful they are, and Chris Rock is appropriating the event for something I don't need to watch. But what choice did he have?" and "If they're disgusting, they're disgusting, and why am I watching disgusting people chuckling inanely? This isn't the gala event it's supposed to be."
And now here's Rock saying "Jada boycotting the Oscars is like me boycotting Rihanna's panties. I wasn't invited." He's calling out Hollywood for racism. How can that work if he doesn't take the higher ground? Here he is gratuitously bringing in the name of a woman, referring not to her as a person, but to her undergarments, for a laugh not about racism, but all of a sudden about sexual intercourse, as if tonight's not the night to concern ourselves with sexism. Rihanna is the human being who's name was chosen to fit that analogy. Why? The joke is written so we'll get it. Rihanna was chosen because we're expected to recognize her as the person Chris Rock would want to have sex with. It's as clear an example of making a woman a sex object as you're going to find. Not only do we get it — because we understand the woman to be sex — but she's not even a woman, she's her panties.
And this is a role given to Rihanna because she was black. As with so many other parts in Hollywood, the role goes to the black person because it's a role that's written for a black person. Rock chose not to complicate the joke with a racial crosscurrent a black man wanting sex with a white woman. A black woman was needed for this cameo appearance — used to insult another black woman (Jada Pinkett) — and that was it for her.