K:

John F. Kennedy:

• Ask not what your country can do for you, ask what you can do for your country.
• We must use time as a tool, not as a couch.
• Mankind must put an end to war, or war will put an end to mankind.
• If a free society cannot help the many who are poor, it cannot save the few who are rich.
• Forgive your enemies, but never forget their names. Let every nation know, whether it
  wishes us well or ill, that we shall pay any price, bear any burden, meet any hardship,
  support any friend, oppose any foe to assure the survival and the success of liberty.
• If we cannot end now our differences, at least we can help make the world safe for diversity.

Martin Luther King, Jr.:

• I submit to you that if a man hasn't discovered something
  he will die for, he isn't fit to live.
• Nothing in all the world is more dangerous than sincere
  ignorance and conscientious stupidity.
• Injustice anywhere is a threat to justice everywhere.
• In the end, we will remember not the words of our enemies,
  but the silence of our friends.
• The time is always right to do what is right.