When they bombed OKC, what didn't happen was that Christians worldwide didn't run out in the streets in celebration and hand out candies and declare the bombers to be heroes. So OKC clearly wasn't "Christian" in any meaningful sense. (Also Christianity has this "Thou shalt not murder" command which would be awfully inconvenient for anyone trying to say the OKC bombing has a Christian theological justification.)
Contrast this to the Islamic reaction to 9/11 - dancing in the streets from Morocco to Indonesia, and yes, even in Europe. Islamic theological justifications for 9/11 are so numerous that I can't even list them all here. Muslims worldwide declared their solidarity with the perpetrators. Islamic governments funded the operation, provided assistance, training, and other support. Imams praised the attacks as the will of Allah... Islamic groups held conventions that called the perps "magnificent". Islamic families named their children "Osama" - for a time that was the most popular baby name in the Islamic world.
Can you spot the difference?
Well said. Although, you're preaching to the choir.