Maester Steven, may I please ask why you describe the Mountain Clans at the outskirts of the Vale as “oppressed” as well as dispossessed? (the latter is objectively true, but given that the Clans outright reject any connection with the Vale that doesn’t involve preying on the local peasants one would argue “Marginalised” or “Exiled” is a more accurate term).

Because it’s standard policy for the knights of the Vale to mount punitive expeditions against the Mountain Clans of the Vale:

“Before that, the chronicles tell of countless battles with the savage mountain clans.” (WOIAF)

“The mountain clans were lawless brigands, descending from the heights to rob and kill and melting away like snow whenever the knights rode out from the Vale in search of them.” (AGOT)

“The clans have grown bolder since Lord Jon died,“ Ser Donnel said. He was a stocky youth of twenty years, earnest and homely, with a wide nose and a shock of thick brown hair. “If it were up to me, I would take a hundred men into the mountains, root them out of their fastnesses, and teach them some sharp lessons, but your sister has forbidden it.” (AGOT)

If we do a bit of de-bowlderization, I think it’s fair to conclude that “root them out of their fastnesses” refers to cavalry raids against camps and villages of civilians, and “sharp lessons” refers to massacres. Hence why the mountain clans have to be described as “savage,” “wildlings,” and the like; de-humanization is required in order to rationalize the gap between the ideals of knightly conduct that the knights of the Vale espouse and how they behave at home.