Yes, although whether or not we find humour in that kind of stuff is is heavily nuanced and context-dependent, even within the narrow genre of kiddie rape and murder.
I think the reason Maddie is such a comedy goldmine is because of the whole circus surrounding the case, and the fact that her white middle class parents blatantly killed her, which *is* inherently funny.
There are other cases where small children were brutally murdered that you'd struggle to find any humour in.
You don't hear any jokes about Jamie Bulger, for example.