This is one of the all-time greatest satires of all time. Swift is attempting to show the inefficiency and injustice of the British officials' treatment of Ireland, which was flailing in poverty. His proposal is ludicrous, eating childrend, but it is presented in a reasonable and humble manner.
First, Swift creates a reasonable, logical solution to the poverty and starvation problems by creating a scenario supported by numerical statistics. Throughout the work, we see his validation of the idea by presenting profit details and logistical support through numbers. His tone is one of a mathematician presenting an economics report.
Second, Swift is humble. He claims that he is not presenting the solution in order to profit himself because he has no children and his wife is beyond childbearing age.