It may convince us, unless we notice that it is based on a hypothetical premise, although the conclusion is not stated hypothetically. Second, if one is in a position to prevent a morally bad state of affairs, without sacrificing something of roughly equal moral importance, one should do so Moral attitudes are shaped by the needs of society, and no doubt society needs people who will observe the rules that make social existence tolerable.
I begin with the assumption that suffering and death from lack of food, shelter, and medical care are bad. If this is an explanation of our common distinction between duty and supererogation, however, it is not a justification of it.
Morality requires that we look beyond our own society because the needs those starving in other societies are just as pressing as our own, if not more so. Now, according to the natural order instituted by divine providence, material goods are provided for the satisfaction of human needs. Singer argues that we should all be morally obligated to give money to humanitarian causes, which means that it is morally wrong to not give money to such causes.
I would now, however, have given greater space to the discussion of the population problem; for I now think that there is a serious case for saying that if a country refuses to take any steps to slow the rate of its population growth, we should not give it aid.
People can hold all sorts of eccentric positions, and perhaps from some of them it would not follow that death by starvation is in itself bad. For a fun take on the essay, see the summary at Philosophy Bro.