Are Trump’s comments really making us less safe? I fear that’s so: Professional counterterrorism experts say that the United States has had relatively few “lone wolf” attacks partly because Muslim Americans believe they are part of the national community. They have a stake in the United States and its security. The FBI and local law enforcement agencies work 24/7 to build this sense of trust and cooperation so that when Muslim communities see extremists in their midst, they will report them to authorities.

These essential threads of interdependence are what Trump is ripping apart. Try to read his words as a Muslim neighbor would, when Trump said Nov. 17, “We’re going to have to look at the mosques. We’re going to have to look very, very carefully.” Or when he responded to a question two days later about creating databases to track Muslims, “certainly” and “absolutely.” Trump’s defenders say he misspoke, or was responding to a question — but that’s precisely the point. He wasn’t being clear and careful, on a subject where clarity is essential in this moment of crisis.

Let’s state the problem in the simplest terms: If Muslim Americans come to believe that prominent leaders (such as the top GOP presidential candidate) view them as less worthy of rights and protections than others, then the job of the Islamic State’s recruiters will become easier. The work of intelligence officers, cops and soldiers who have been trying to stop our terrorist adversaries will become more difficult.