President Donald Trump delivered what sounded like one of his typical meandering, grievance-laden campaign speeches on Friday, but it was where he did it — inside the U.S. Department of Justice — that mattered.The appearance marked Trump’s clearest exertion yet of personal control over the country’s federal law enforcement apparatus, which is normally run by appointees who keep at least an arm’s length from the president to avoid the appearance that politics are governing prosecutorial decisions. Trump, instead, embraced the notion of the agency as his own personal tool of vengeance.The appearance marked Trump’s clearest exertion yet of personal control...