Correct. Stannis could strike a bargain to take X number of Wildings somewhere beyond the wall for X number of Wildling soldiers after they stop the White Walkers. If it were me, I'd drop a number of Wildings in the Iron Isle and tell them they can live there if they can conquer it. Are the Wildings trying to get south just because of the coming Winter or because of the Walkers?
Keep in mind, the Hound killed the wounded old man at the farm to put him out of his misery. Mercy killing isn't totally out of character for him, although I think that's was a new facet of his personality.
The 1st was a farmer and his daughter. Remember they made the rabbit stew that Sandor and Arya just swallowed. The farmer offered Sandor pay, room, and board in exchange for silver. In the morning, Sandor kicked his ass, took the silver, and left. Arya protested, and Sandor gave the speech "He's already dead. He can't protect himself or his daughter. He's weak. And the weak die."
The 2nd was either a farmer or soldier. They encountered him while traveling. Arya mercy killed him. And then Sandor got jumped by 2 idiots. 1 was unarmed (he went first, where is even more stupid) and bit Sandor in the neck. The other was one of the 3 in the cages going up to the North with Yoten. 1 of the 3 in the cage with Ja'qen. The other 2 joined up with Tywin's army, and now just are raiding in the Riverlands by themselves. The ugly guy stays back (with his sword, letting the unarmed guy go after Sandor first), Arya recognizes him, they exchange words, she stabs him.
Okay, I'm not sure what the difference is, but I wouldn't say it puts Sandor, The Hound in high moral standing. Also, thanks everyone for the repeated use, sincerely now, of Sandor, as I couldn't remember that was The Hounds' true name, and I frustratingly enough still remembered Podrick saying it to Brienne in The Children.