In "A Modest Proposal" why does the narrator express the hope that his plan will not be liable to the least objection just before he introduces it?

In Swift's "A Modest Proposal," when the speaker says
that

I shall
now therefore humbly propose my own thoughts, which I hope will not be liable to the
least objection....

he, first
of all, is literally saying that he hopes no one will object to his proposal.  This
makes sense because he is proposing something that he supposedly wants others to approve
of.  He would naturally want everyone to
agree.

Figuratively, of course, the speaker is being
ironic.  He says he hopes no one will object, because he knows everyone will object.  He
uses this kind of irony throughout the essay, starting with the title:  his proposal is
anything but modest.

That's the long, official answer.  The
short answer is that he's being funny; making a joke.