in part 2, what might swift be criticing through the actions of the farmer?

It almost sounds like he's making a parallel between the actions of the farmer putting Gulliver on display and what they used to do in "freak shows." Gulliver would have been a curiosity, and if you go back in history and look at the freak show, people who were different (and most of them very different) were used to make money. People will come to gape at things that aren't normal to them. Gulliver could make the farmer rich, and the farmer knew that.