Slyder, just out ride the little turd in front of his friends. If his friends ask for tips or how you learned how to that steez (btw its reciprocal ask his friends how they do some trick), tell them but not him and they will correct him. Thus you don't have to put that strain on the relationship. I would actively ask my daughter's friends about doing things (on the drive to the hill and on the hill) and they were quite helpful...I try doing some thing...and at least get lots of rad points for the old geezer at least trying.
One of my finer examples of this psychology...watching the kids hit this little windlip, me asking lots of questions and then hitting it...they talked about this example for a couple of weeks.