I'm sympathetic towards anyone who is murdered.
This, including those murdered by religious extremists--whether Muslim extremists, Christian extremists, or anyone else.
If there are any Christian extremists in the Middle East, I'd love to hear more. It's kind of hard for a group that only makes up less than 5% of the population to have the means to commit acts of violence against the majority. Same goes for the Druze, the Armenians and other minority groups.
The only example of Christian-on-Muslim violence that has happened there since the Crusades was during the Lebanese Civil War in the early 1980s when the Phalangists massacred large numbers of Palestinian Muslims and Lebanese Shi'ite Muslims (in many cases with the tacit help of Israel). But even that can't really be blamed on religious extremism since the Phalangists were a secular Fascist movement that viewed Lebanese Christians as ethnically distinct from the Muslims and were acting out of a perceived need to preserve their ethnicity/culture, rather than doing "the Lord's work."