"I'm going to smack your face down... monster card..." Chris is an aversive racist: he knows next to nothing about actual black people (as evidenced in the Lars Call) and therefore fears them, and things that he fears getting up in his space make him BLANGRY and loose-boweled. His ignorance-based racism is also why he had no idea that "Ching Chong" was a super-common racial slur for Asians, and why he thought that Jewish people enjoyed being given single, candle-shaped cookies on other people's holidays. When anyone but white people enters his mental space, including the kids he accused of stealing his Pokeymans (and of course Marvin in his snazzy brined-cucumber suit), he gets confused because it's so off-script for his life in general. (Question: Has anybody spotted one kid of color in photos from his school years, up to and including that prom/graduation dance thing?)