I wouldn't say racist but he knew his fanbase was mostly white guys.
Chael Sonnen popularity wasn't just because of the trolling, it was because alot of the UFC Fanbase hated Anderson Silva...I know Anderson Silva gets lots of love today but that wasn't the case back when Sonnen faced em..Silva was legit hated....Then Came Sonnen, talked shit about him/Brazil/etc.....The UFC Fanbase loved it, the fanbase, specially back then was mostly Young White guys.
Sonnen was suppose to be the hero who was suppose to save the UFC from Anderson Silva.....Boi were they wrong lol.
He even called himself a republican and called himself the American gangster, very appealing to the Young American White guy fanbase....Not saying that's not who he is, but that probably appeals to American Young white guys who follow him.
Im not sure if Chael ever said anything racist(he did say Brazil Jokes) but I believe he knew his fanbase was made up of many Merrican racist....Which is why he also talked shit about brazil/japan, it appeals to the typical Merrican racist.