Lots of people tweet memes without checking who made them. The president of the United States — or someone close to him who manages his social media account — seems to be one of those people. On Sunday morning, President Trump tweeted out a doctored old video of a professional wrestling match in which he, appearing in character as himself, pummeled another performer and sent them to the ground. Except someone had replaced the other wrestler’s head with the CNN logo — a jokey meme that reflects the president’s long-running feud with the cable news network. But Trump didn’t create...