1. Abnegation are chosen to be the political leaders of society because they are the most selfless of the factions, and therefore it is thought that they will do what's best for the good of the people and will not be corrupted with power.
2. Jeanine Matthews is the sole representative of Erudite, and Beatrice's father has a dislike for her because she released a report attacking his political partner, Marcus. I believe his actions are not warranted because there is evidence supporting that what Jeanine claims Marcus did to his son, Tobias, is in fact true. However, Beatrice's father does not believe that Marcus is capable of being cruel because of his faction.
