The Trump Administration has frozen billions in federal grants to Harvard University, threatened its tax-exempt status, and sought to dictate its curriculum and hiring. Now the government seems bent on destroying the school for the offense of fighting back. And for what purpose? That’s how we read the Department of Homeland Security’s move Thursday to bar foreign students from attending the world-renowned institution. That’s 6,800 students, or a quarter of Harvard’s student body, whose futures are suddenly in disarray. It’s also a short-sighted attack on one of America’s great competitive strengths: Its ability to attract the world’s best and brightest....