They would have to climb up a rung or two just to qualify as downtrodden. Whenever you issued peasants or peons (the Horde's worker unit) an order, they would reply "Okay" in an utterly dejected way, as if they had already resigned themselves to some horrible fate. Peons, I could understand, before they're clearly treated like total crap by the rest of the Horde, but there's never been any indication that peasants are being actively oppressed in the human kingdoms. Maybe it's the fact that they're conscripted to build sprawling base after sprawling base, chop down tons of wood and work in mines that's worn their spirits down to nubs. It certainly can't help that they're also under constant threat of raids by the Horde and since they play an unappreciated, but vital role in the Alliance warmachine, they're naturally targeted. I mean, are these guys even being paid for their contributions?
I'm surprised there weren't peasant uprisings during the Second War. Maybe there were and they were brutally suppressed?