How do you deal with racist relatives ?

My MIL & I clash consistently because of derogatory terms, assumptions etc made about strangers based on their skin color. I don’t think there’s room for silence on important issues like this. You can’t change everyone’s opinions or behavior but you can expect that if you two differ on that issue that there’s no need to talk about it. If she feels the need to speak poorly of whoever then she’s giving the green light to speak up against that.