If I may add some levity to the situation......if a player is to dunk during warmups/halftime....at least MAKE IT.
Seriously now, I reffed a JV Boys several years ago. During halftime, one of the JV players (not varsity) tried to dunk. The kid was an athletic high jumper type so I think he was just trying to see if he could get high enough to dunk the ball rather than show off.
My partner didn't see it, but I did. After thinking about it for a second, I decided to assess the technical. THe JV coach was a little surprised I would T the kid for that. However, I figured it would be a good lesson.