How the media can defang poisonous political discourse

Following the shooting of Rep. Gabrielle Giffords (D., Ariz.) Saturday in Tucson, many people asked: Did the violence of U.S. political rhetoric have anything to do with this? Did a gunman try to kill Giffords because there is so much toxic language, such hate in our political discourse? And if our discourse is toxic, what should change in the way we talk, the way we disagree?