I had my share of those, especially when I first became head of the band program. One in particular kept giving me lip about my evening rehearsals and how they were interfering with their child's other activities (his girlfriend). I got fed up with him and offered the parent my keys, charts, and mic. Told him that he was welcome to take the program if he felt he could do better. He immediately backed off. When I got the eventual call from my FA director, I explained exactly what happened. He backed me up.
(I'm not condoning this. I was in a position where I had other options if need be. But man, was it fun!! Didn't have any issues after that. The kid ended up leaving band).