I have seen the warning signs for mass atrocities before in a career that took me to war-torn places like South Sudan. Now I see them again, right here at home in the United States. Here is some of what I saw then, and some of what I'm seeing right here, right now. On July 7, 2016, while I was a diplomat supporting a peace agreement in South Sudan, my close American colleagues were repeatedly fired upon by South Sudanese troops as they drove past the president's residence. For the next four days, the South Sudanese government and rebel armies...