«On the subject of the salt merchants profiting at the expense of the peasants, they are in agreement.»

Indeed. And I'd guess Dog Fox doesn't prey on the peasants -- who have little anyway and may sometimes be friends or allies, at least to the extent of "not having seen him" when Imperial or other officials come snooping.

Which means he probably targets merchants-- maybe sometimes salt merchants-- and the occasional rich traveler. Though the latter is risky, since you never can tell who might be high-ranking enough to make real trouble for you, especially if they travel under an alias, unlike Ju Lee here.