How conveniently you forget about all the Christian attacks on black people--can you say "lynching"?--and what about all the beatings, rapes, and murders of gay, lesbian, and transgendered people--all justified in some twisted way by the Christian Holy Book. Maybe killing queers doesn't seem like terrorism to you but it does to us. It's all a matter of perspective, members of Islam probably don't see their attacks on us as terrorism, but we do. Even the most casual examination of Christian history will reveal that Christians have been visiting Hell on Earth on people they don't like--including each other--for nearly 2000 years. Islam didn't run the Inquisition, Islam wasn't responsible for the Dark Ages, and it wasn't Islamic crazies that burned 10's of thousands of women at the stake over a 500 year period all across Europe.
And I'll bet--just a guess on my part really--that the thousands of Iraqi civilians (the women and children at the very least) whose country has been bombed into the stoneage probably view us "Christians" as terrorists.