Thirty seconds into Howard Schultz’s first campaign event last Monday in New York City, one attendee yelled “Don’t help elect Trump, you egotistical, billionaire a—h—!” The shouter was joined by thousands of vitriolic posts on social media. The mainstream media, which thrives on tribal warfare, added fuel to the fire, urging Mr. Schultz not to run for president.

All this happened before anything was known about Mr. Schultz’s positions or vision for the U.S. Instead, Democrats attacked him for potentially “spoiling” the 2020...