That Malthus population principle is at the heart of the environmental/deep ecology movement also. A doctrine of “reduce the population by some means because there will never be enough for all.”
And as you say, pernicious because it seems logical. Draw a graph with lines showing this and such, all very reasonable looking and wrong.
Malthus's theories have been modified or adapted in various ways by neo-malthusians and communists. But Malthus's original full-strength theory is the insanest of all, and it is that theory which Darwin relies on for natural selection to work. You see, Malthus believed that populations are not just tending toward their maximum level of sustinence. The geometric growth is such that populations are always at their maximum level of sustinence, and, as a consequence, they are plunged into inescapable vice and misery when they go beyond it. Right now the paupers are beyond their maximum level of sustinence and that's why they are miserable and vice-ridden. Any more babies they have incurrs more punishment of this natural law that doles out more misery and vice to them. This isn't a catastrophe to happen in the future. It is supposed to be happening now and always. The purpose of his theory was to explain why the rich class existed alongside a huge class of miserable vice-ridden paupers in England, and what to do about it.