"Man, that ho at the club was grinding on me for like two hours, then she left with my friggin' roommate! I gotta' go beat the brains out of the little soldier!!!"
It is commonly known that the in the minute an individual dies, any feces in the body will immediatley leave due to intens rectal relaxation, so when saying "I will beat the shit out you" you are suggesting that your beating will result in death and rectal discharge of fecal matter