Yeah, and I wish Arma allowed that too. But you sure as hell won't be acing a game with that unless you choose your missions, enemies, and encounters so exceptionally carefully that nobody probably will even hear of you. There's a huge difference between using a knife when appropriate, otherwise the gun, and only using a knife when everybody else serious is using guns with likely proper tactics. War doesn't miss one man these days. Any grunt with an assault rifle is far more dangerous than the most fit, trained, and well equipped knight of the times long gone.
The jedi in Star Wars managed well enough with lightsabers because they had the magical force powers. Is Kirito supposed to have such? Why would the game allow such? Even if he hacked the game, it should be a proper game with proper admins this time and when somebody runs around deflecting bullets or dodging them, it should gather the server staff's attention.