Closer to the latter, but probably neither. While 18th century satirists certainly weren't above calling their rival's work shitty in clever verse (see Pope's Dunciad), Swift's preoccupation with bodily functions and personal revulsion at them seems to go a little beyond. The Lady's Dressing Room is a telling example; see also A Beautiful Young Nymph Going to Bed.

Edited to add: Swift wasn't above fart jokes, either--I refer you to this. But the section of Gulliver dealing with the Yahoos shows us that Swift has trouble reconciling the more "disgusting" bodily functions and animalistic behavior with our potential to be good and wise.