Authorities have confirmed that an apparent bomb addressed to Maricopa, Ariz., County Sheriff Joe Arpaio was uncovered and diverted, and now investigators are beginning to look into a list of his enemies for any links or connections. Those who have had conflicts with him, those who might be coming under investigation, those who have been unsuccessful in fights with him. That should be a job. Arpaio, who has described himself as the “toughest sheriff in America,” has had conflicts over the past few years with advocates for illegal immigration, those who don’t like his enforcement of state laws in Arizona,...