From a practical standpoint their linkage is clear as interchangeable and classic mass movements, requiring and inspiring unity and self-sacrifice. The respect given to Islam as "religion" is a distinction without any true meaning.
Anyone who has bothered to read Eric Hoffer's The True Believer, or The Passionate State of Mind, for example, would see their interchangeability in an instant. Had it been required reading (as it was in the Eisenhower and Kennedy administrations, before political correctness erased Hoffer - who had no formalized education - from every syllabus until Ronald Reagan awarded him the Medal of Freedom in 1983) during the Bush administration our policy in combating Islamic terror would have turned out quite different and perhaps effective.
Cheers!
The second monster in the image of the first monster, in the image of the second monster. Evil eternal. God will sort things out. He’s that good!