Sallust

"All those who offer an opinion on any doubtful point should first clear their minds of every sentiment of dislike, friendship, anger or pity."

"To like and dislike the same things, this is what makes a solid friendship."

"The firmest friendship is based on an identity of likes and dislikes."

"All who consult on doubtful matters, should be void of hatred, friendship, anger, and pity."