(Does merely pointing out the irony of Mr. Kirk’s opposition to gun control count as “making light”?) Some of the commentary about Mr. Kirk from the right has been appropriate and inarguable. He might have added that calling political opponents “un-American” or “treasonous” (as Mr. Trump has repeatedly done) is also playing with fire. And claiming that a sitting president does not “love America,” an accusation made against President Obama by Rudy Giuliani and others, does not exactly turn down the temperature. Whether or not you agree with their conclusions, that discussion needs to continue—not despite but because of the threat of political violence.