I don’t think anything other medium is labeled as an opinion. I don’t think people typically on medium label their pieces as opinions. I just take them all to be opinions. But I would hardly say he’s making extraordinary accusations. Instead, he’s probing some of the central ideas behind racism as a thought experiment. I don’t think these are extraordinary claims. In fact, I find many of his claims to be merely a list of the things I myself of studied. They were ordinary claims listed in a nice manner.
But if you’re offended, you can be. That’s the great thing about opinion pieces. People can take as much offense they want. Or as much insight as they want. And then walk away.