I have been to baby showers where they melt different candy bars into diapers, and the game is that guests have to try to identify the correct candy bars.

The visual effect is very convincing; the women who always win the prize are those that can screw up their courage and actually take a bite; most people can't bring themselves to do it.

I think in this case, an adult asking a child to face what surely very much LOOKS like shit in a diaper, it's beyond the pale, even if done in humor.

However, I'm not sure he should have lost his job over it. I think he could have been officially warned or whatever. Now, if he'd used actual shit, he should have been arrested.