Diverting a flight for a non emergency situation to prove a point for 1 or 2 self upgrade passengers or not having the mask on all the time is a new low.
why make suffer the rest 100+ passengers?
Why not have police wait for him/her upon arrival and ban him/her from future flights?
This only makes everyone unhappy and results in lost of revenue to the airline industry. I would set up in each airline a small department that deals with this petty stuff, so a pilot would have to first consult with airline to return a flight for this type of non life threatening small petty stuff.