it's people being dicks. plain and simple, it's assault.
i can steal a purse in the park - it's robbery. it's not "the old lady handbag game".
One can commit rape. It's rape. It's not, "Surprise half-consensual quickie time".
seriously, "knockout game" is a media creation. It's kids assaulting people. it's not new. it's not a game or funny. it's assault.