#OnThisDay in 1963 excerpts from MLKing Jr's Letter from Birmingham Jail were leaked in NY Post's Sunday Magazine. King wrote the letter as a response to "A Call for Unity" by 8 white clergymen who disagreed with King's methods of protest (b/c "you can protest, just not like THAT" is a common refrain in the fight for social justice). The letter included the oft-repeated line: "Injustice anywhere is a threat to justice everywhere." #HistoryGetsLIT