They couldn't just murder him, he's a Lannister. What they were doing was already pushing the envelope mega time, and I feel like part of it was meant to show how Stark's sister and that part of the kingdom is crazy

Which reminds me, why in the shitballs didn't they dye the pImp's hair blond? Family/color is an important distinction they're making. My guess is that him being a drawf makes him genetically acceptable for not fitting the mold