Trump's instinct — to slam the brakes after the horrific National Guard shooting by an Afghan migrant — is understandable. Any leader with a conscience wants to shield his people. The country is rattled, grieving, and wondering how a young man welcomed into America's care ended up turning his weapon on Americans. Trump sensed that fear and moved swiftly, promising a halt to migration from all "third-world countries." It's blunt, straightforward, and politically explosive. But good instinct isn't the same as good judgment, and this is where his approach deserves scrutiny...