That's the thing: He was an infidel first.
If this stuff about him being a terrorist sympathizer is true, it would hardly matter to Zarqawi. His mission is to kill all the infidels. Nick berg was an infidel. Whether he was an infidel who was interested in appeasement was not really a factor.
He was an infidel first.
And he was sacrificed, per the manual, to the blood god...