I'm under the impression that the group is a secular Marxist group so the religious connotation sounds a bit odd to me. They were affiliated with Popular Liberation Front of Palestine, but that front is also outright secular (and there were both Christians and Muslims in that group) so JRA can't be influenced by them.

I'm completely out of the loop of the leftist movements in the 70s however - so I don't know if 70s leftist tactic (or maybe leftist political thought) actually has something to do with the use of religious metaphor.