One that often comes to mind when reading political debates on the internet is by Bertrand Russell: "Collective fear stimulates herd instinct, and tends to produce ferocity toward those who are not regarded as members of the herd." Another one that has stuck with me for a long time comes from Calvin Coolidge: "Nothing in this world can take the place of persistence. Talent will not; nothing is more common than unsuccessful men with talent. Genius will not; unrewarded genius is almost a proverb. Education will not; the world is full of educated derelicts. Persistence and determination alone are omnipotent."