Why do politicians want to take away our plastic bags and straws? This moral panic is intensifying even as evidence mounts that banning plastic is both a waste of money and harmful to the environment. If you want to protect dolphins and sea turtles, you should take special care to place your plastic in the trash, not the recycling bin. And if you’re worried about climate change, you’ll cherish those gossamer grocery bags once you learn the facts about plastic.

During the 1970s, environmentalists wanted to restrict the use...