Twitter has provoked outrage. But Trump is the bigger problem.

TWITTER HAS provoked outrage for its refusal to remove disgraceful tweets from President Trump that further a baseless conspiracy theory about the death of a former congressional staffer. Whether anger at the social media site is justified, the debate shouldn’t obscure the obvious: The bigger problem is the president.

Twitter provided only an apology this week to the husband of Lori Klausutis after he petitioned the company to take down the “vicious lies” Mr. Trump has spread about his wife, who passed away in 2001 when she fainted and hit...