They're avoiding the elephant in the room if they don't talk about race.
Whether or not you want to admit, race is a central topic and issue within our society. It's hard not to have a strong opinion on the killings, the inequality and the polarising nature of politics.
If it is not discussed with your partner, it is for the same reason you don't discuss politics and religion with guests, you're frightened of the fallout. If you're frightened of the fallout when it comes to racial issues, that should raise a few questions but who am I to question the decisions she makes in her life.