street scene night dad & kid(s) coming out of a martial arts class accosted by a guy who says, "hey daddy, are you gonna be a hero and go all ninja on me-- --or are you just walking around in your pajamas?" dad's voice quavers but he stands up to him but the guy kicks the shit out of him while kid(s) watch(es) kid says, "daddy, why didn't it work?" How does he explain it?