It’s a familiar story, a boat or plane accident causes a group of people to be stranded on an island. There is little fresh water or food. The plot centers on the response of the victims as they strive to survive with limited resources. Search parties scour the island for food and water and others look for ways conserve what they have.
Imagine if one of the survivors suggested that the strong among them kill off the weak so the scant resources would last longer. How would they be viewed by those reading the story?
That person is scum would be the opinion of many.
That suggestion, kill off the weak so there are sufficient resources for the strong is exactly what the overpopulation crowd is preaching. They cite statistics to back up their claim that the Earth lacks sufficient resources to support the number of people alive today or predicted to be alive in the near future.
Through Birth Control, Abortion, and Euthanasia, they propose to re-balance the Earth so the strong (they are among them) can live in prosperity.
Their arguments are allowed to be discussed logically because of the global nature of their plans. But if we shrink their hypothesis to a desolate island and call their procedures what is, Murder, well, such talk is not Politically Correct.
It all comes down to who is allowed to live and who must die. Sounds brutal because it is.