Thor-son-son-Vallano

So I remember watching Sanderson doing a youtube video and in it he answers questions and someone brought up when is the sequel going to happen. I swear he said something along the lines of I still haven't figured out how to get rid of the racism in it. I wish I could find that video again but ever since I can't find it again. Ever since hearing that I can't think of how or what is considered racist in it.