George W. Bush gave Democrats a gift this week—which should be a reminder of the perils of demonizing political opponents. But don’t bank on the left accepting his gracious offering.

Promoting his new book about veterans on NBC’s “Today” show, Mr. Bush was asked to weigh in on the fight between Donald Trump and the media. “We need an independent media to hold people like me to account,” he told Matt Lauer. “Power can be very addictive and it can be corrosive, and it’s important for the media to call to account people who...