Why do apologists for terrorists find it impossible to live in the current century?

the Crusades are the reason for Jihad. never mind that the Crusaders are long dead and buried(or burned) I'm always amazed at the vast numbers of people who will use history as justification for the most obnoxious behavior. I had a guy one time tell me the Confederacy was justified in firing on Fort Sumpter(1861 because General Sherman invaded Georgia!(1864)