Can the FBI Stop the Trump Extremists?

The president's backers are openly calling for sedition, secession, even murder, while police struggle with sympathizers in their ranks

Last month a young Georgia man and his girlfriend were stopped by Washington, D.C. police as they sauntered across a broad city intersection carrying compact semi-automatic weapons. A search of their hotel room turned up additional weapons and ammunition, including an “unusual”  loaded submachine gun, according to an account in The Washington Post. 

The …