It might sound silly, but my reasoning is that there was a farm JUST OFF THE EDGE OF THE MAP.
Okay, but my feeling is that if you're going to place an Innocent who couldn't even take out a Kobold in an area filled with very dangerous Hostiles (as Peldvale is), then there should be at least
something supporting it, something beyond a dialog that BioWare chose to cut. True, you could stick him in the NW corner that is (questionably) "protected" by the Flaming Fist Officer, but I think even that's asking a bit much. Not that
my suggestion has any great merit either, of course.
Regarding the "you'd better not have had any part in polluting this area" bit, "area" could mean anything from a few square feet to a few square miles. Wrym's Crossing is only a few miles from Peldvale, and so the lands just southeast of the Gate might very well be considered to be part of the same "area," especially if you've already walked across them once today and are about to make the round trip.