Taking the "The Modest Proposal" seriously, is the premise of the argument, selling and eating babies to get rid of famine and overpopulation, a sound argument?
If you were to assume that you could overcome the problems inherent in expecting parents to give up their children knowing that they would be eaten, and of course expect that people would be willing to cook and eat babies, it would still not be a viable solution to the problem that faced the Irish people at the time.
If you consider the law of conservation of energy, you cannot create energy (in this case calories) from nothing, the mothers have to be able to eat to feed the babies and in so many cases, the mothers had nothing to eat, or certainly nowhere near enough. When you look carefully at the population numbers in Ireland pre and post famine, you see the magnitude of the problem and the fact that even if it were possible to take it seriously, Swift's solution was no actual solution.
Arguably the only serious solution to the problem would have been to force British landlords to stop exporting all the crops they continued to export throughout the famine which would have provided significant relief to most of the Irish people.