The speaker is a scientist presenting a learned discussion paper, the kind that would be put before the Royal Society, Great Britain's national academy of sciences. Swift was scathing of many of the ideas put forward at the Royal Society, which he saw as useless, dangerous, or, in some cases, both. And it's just such ideas that he's satirizing in "A Modest Proposal".
What makes the "Proposal" particularly effective is the empirical language it uses, exactly the kind of language you'd see in a scientific paper. Though the ideas advanced in the paper are truly revolting and morally reprehensible, the scientific language in which they are presented gives them an academic credibility and respectability which they simply don't deserve.
As the paper's central thesis—that children should be bred for meat—is so disgusting to all right-thinking people, it needs to be cloaked in the bloodless language of science to make it more palatable. If the paper had been written in the style of a polemic, then it would've been rejected by just about everyone. But because it's couched in the language of a learned scientific paper then more people are likely to stop and think that maybe what's being proposed isn't such a bad idea after all and should therefore be given due consideration.