Reply #19: I view the meaning as strictly compositional.

[Igel]

German fascism is the variety of fascism unique to Germans, or that found German-flavored expression. It's not saying all Germans adhere to it. I don't know that I'd accept the phrase "fascist Germanism". I don't know what 'Germanism' is (just what it could be).

Islamic fascism is the variety of fascism unique to adherents of Islam, or that finds an Islam-flavored expression.

I guess I could allow "fascistic Islam", but that is ambiguous between attributing the properties of fascism to Islam as a whole--precisely what we don't want to do--and selecting out that kind of Islam with fascistic attributes.

"Islamic fascism" could be saying that an attribute of fascism is Islamism/Islam, but that's obviously false. So it defaults to selecting out that kind of fascism that has Islamic properties. Squirrelly phrase, and there are reasonable alternatives, but they're no more palatable. So I go with the expression that has some currency.