Via RollCall, Luisita Lopez Torregrosa, a journalist and writer based in New York City, is a professor at Fordham University:For the second time in more than half a century, Dallas is at the center of a seminal moment in our history. It’s a moment set against imploding national anxiety and anger, stark racial divisions, black-and-white outrage and violence that haunt us.  If ever the phrase “Things fall apart; the center cannot hold” fits a time, this may be it, a moment that perhaps more brutally than other horrifying racial tragedies in the past few years exemplifies the devolving breakdown of America…For Dallas, this was a recurring nightmare, dredging a dreadful past when the city was known worldwide as the “City of Hate” after the assassination of John F. Kennedy there on Nov. 22, 1963…Today, (Dallas) is a vibrant majority-minority city, 42 percent Latino, 28 percent white and 25 percent African American.  Blacks have served as mayor and local officials and now chief of police. Dallas votes Democratic, has more than 1.3 million people and ranks among the top 10 biggest cities in the United States…”