I doubt that Jared Loughner who is accused of killing six people (at last count) in Tuscon, Arizona could be described as a Christian. However, he could have been influenced by Christians who hate everything secular about the big government society of the United States of America.
Would we call someone who is white and celebrates Christmas in one way or another a Christian terrorist? I doubt it. People will call that person a terrorist or insane, but not a Christian terrorist.
What's wrong with Christianity?