There's more though. Check out what the actual Karens on the show, the "White" female actresses, said to defend the episode (from the same article):
The stars who played Pam and Angela, Jenna Fischer and Angela Kinsey, respectively, addressed the racism in the Benihana Christmas episode on their podcast, “Office Ladies.” They agreed that the scene in which Michael draws on the Asian woman made them “cringe.” However, they provided a different explanation for the character returning to the party with two other women. “The idea here was simply that Michael and Andy couldn’t land the original waitresses that they’d been flirting with all night, and then they manage to get these two younger, kind of more naive waitresses to come back with them to the office,”
But why did he think the naive waitresses would be a suitable substitute for the real ones? Because they are "Asian"? If he were courting a "White" woman and didn't manage to land her, would he have brought an unattractive "White" woman in as her replacement? And if not, why not? Is it because he thinks it is because all "Asians" look the same, and therefore it would be hard to spot the difference, but all "Whites" do not look the same, and so therefore it would be easy to tell the difference?
BTW, how do we know Carell is a racist? Couldn't it be that he was just reading his lines? If so, isn't this the fault of the writer/director?