That makes sense.
People waging terrorist campaigns for ostensibly religious reasons should be distinguished from other terrorists.
But they both remain terrorists, and the point of the article then becomes apparent - there are more terrorists who are not Muslim, overwhelmingly more, than there are terrorists who are Muslim.
But the former have my sympathy because they fight against injustices meted out to them and they want to right the wrongs of the past done by some oppressive state/central governments. Their fight is localized and will end once they get justice.
The latter fight because they want global superiority and a hegemony over others. Their fight is everywhere. A Chechen who was oppressed by the Russian government, does not mind taking it out on the runners of a marathon in Boston. They do not have my sympathies.