I mean, Slytherins have to be the best house at diplomacy because we're the only ones intelligent enough to know how to and good at interpersonal relationships, but still cunning enough to know how to get what we want.
It is just that Slytherin has a longer list of dark wizards. Gee, I wonder why. Maybe they are treated like trash by the other three houses and want revenge. Who would have thought that Slytherins have feelings as well?
I loved reading this on Pottermore. Draco had been parroting what his parents had said for so long and never really understood what it meant. Until he was put in that position, and realized that he wasn't a killer, that
she cared more about the safety of her family IN EVERY BOOK SHE IS FEATURED IN than any kind of war or cause! for her, the love for her family was the most important thing of ALL!<<And don't forget about Regulus!