It is getting to the point where no jokes at all can be permitted. Any and every subject has someone, somewhere, who will link any mention of it with their painful situation. This has always been the case and it always will be, unless all but the most anodyne of jokes vanish completely. It seems to me that we would all find that incredibly boring and flat.
Analysts of why humour is funny (a good way to kill all the fun!) say that the reason a joke raises a laugh is because of the unexpected connection made between two unconnected things, releasing the tension between what is expected and what is said. Linking some everyday comment with something in the news does that. This is why there are always jokes about news items and people in the public eye - the juxtaposition of serious comment with some mundane observation takes the hearer by surprise.
In this case it was child abuse - which is so emotive a subject that it makes people feel uncomfortable if they laugh, but it was still a link of cubs with Cubs - mundane with serious.