In 1948, Association of Comic Magazine Publishers (ACMP) was formed by some comic publishers. The goal is to set guidelines for comic books to be published and reduce the criticism against comic. They set a board of people who will approve the comic before sent to print.
Just before that, a mass burning of comic books happened after a house to house collection was made by the citizens of Binghamton, New York on December 20th 1948. It was reported by Time magazine including a photo of that event with kids watching in the background.
Dr. Fredric Werthham was the scariest thing happened to the comic culture. He was a highly distinguished psychologist who thought comic books were bad for kids and effort to totally ban had a lasting impact until today.
He studied children and wrote in his book Seduction of the Innocent that comic is the major cause of juvenile delinquency. He also stated that comics gave wrong ideas about physics laws because Superman could fly, Batman and Robin characters re-enforcing homosexuality and Wonder Woman was giving little girls the "wrong ideas" about a woman's place in society.
REFERENCE : http://www.psu.edu/dept/inart10_110/inart10/cmbk4cca.html