South Park: Bigger, Longer & Uncut (1999)

Continuity mistake: During the "La Resistance" number, during the verse, "They may stab you in the head, with a dagger or sword," We see a guy wearing blue with a blue hat on the left (probably Craig). In the next shot, he disappears, and in the next shot, he reappears. (00:50:05)

General: Now each battalion has a specific code-name and mission. Battalion 5, raise your hands!
[All of the African-Americans raise their hands.]
General: You will be the all important first defense wave, which we will call "Operation Human Shield."
Chef: Hey, wait a minute!
General: Now keep in mind, Operation Human Shield will suffer heavy losses. But don't lose your spirit, men! Stay until the bitter end. Battalion 14?
[The rest of the group, all Caucasian, raise their hands.]
General: Right, you are "Operation Get Behind The Darkies." You will follow Battalion 5 here, and try not to get killed for God's sake! Are there any questions, men?
[Chef raises his hand.]
General: Yes, soldier?
Chef: Haven't you heard of the Emancipation Proclamation?
General: I don't listen to hip-hop.

Question: When Cartman says he saw Kenny, Kyle says he sees Kenny everyday, on the face of every child, on the smile of every baby and he and Stan starts laughing. What does the joke mean?