As presumptive Republican nominee Donald Trump arrived in Cleveland Monday afternoon, he was greeted by NBC Today co-host Matt Lauer hectoring him about the “tone” of the GOP convention, which had barely started: “There’s been so much violence in the country in the last couple of weeks. People are on edge, they’re tense. You add to that the passion that comes with political debate and there are people who are truly afraid that things could boil over here in Cleveland.” In the interview, aired on Tuesday morning, Lauer demanded Trump promise to keep convention speakers in line: “Would you be...