Without causing offence most people who ridicule getting your knee down are those that can't. Wheelies, stoppies and knee down are all about advanced control and aren't really for the road, and why then do racers do it at all if it's to be rubbished. That said there is no reason not to want to learn new skills in the right environment. Learning to corner properly with position and counter steering should be mastered first along with entry, apex and vanishing point. Exagerated head position looking through a corner assists in counter steer naturally. Gear selection and body posture will dictate knee down before reaching your tyre limit. Possible to get your knee down sweeping the width of a motorway and not far from upright.