The day before, my wife, Susan, had rushed into our apartment, shaking and with both fists clenched. Through tears, she told me about the shootings at Rep. Gabrielle Giffords’s meeting at a parking lot in Tucson, Ariz. “So help me, God” were the first words of an outburst that included many harsh words for politicians and talk show hosts — public figures whose invective had turned politics into a rhetorical killing field. For Susan and me, the attack hit too close to ...