A Duke University professor criticized for his response to an editorial on racial issues says he doesn't believe that it's racist to compare blacks and Asians.

Political science professor Jerry Hough said in an email to The Associated Press on Monday that he frequently responds to columns and editorials. He says he doesn't think his response to a May 9 New York Times editorial was racist.

In the response, Hough compared "the blacks" and "the Asians." He wrote in the online comment section that Asians faced racism but "worked doubly hard."

He said that subtlety is sometimes lost in short pieces and that there's a word limit on comments on the newspaper's website.

University officials say Hough has been on a standard academic leave for the 2014-15 school year.