The answer is: He states that sending children to the butcher would be as simple as “roasting pigs.”
An understatement is a statement that presents something as being less relevant, less important or smaller than it actually is.
In this case, the understatement is that roasting children is just as simple as roasting pigs. Swift, the author of <em>A modest Proposal, </em>is a master of satire and the many uses that it acquires, this being one. This essay is a perfect example of his satire. In it, Swift recommends that Irish children be put to death and fed to the rich people in order to ease the latter´s big appetite and “help” the Irish alleviate their poverty by selling off their children as food.