There's probably a term for this in the study of logic/forensics/debate, but not knowing any better I can only describe it: there's a technique often used by the left that attempts to define concepts out of existence by their failure to conform to a precise, non-arbitrary and unambiguous delineation.
The "there is no such thing as race" argument is one of these, because true enough there's not a precise boundary between different human groups. But it's rather like saying "there is no such thing as color" because there are infinite gradations from one to the other, and red becomes purple becomes blue at points that are necessarily arbitrary. It would be foolish to say that red and blue are invalid concepts because of this.
It is the same with the Islamic threat. The left have taken their usual position, arguing that "Islamic terror" is a far too amorphous concept. So, accepting this premise, how can it be treasonous to accept money from an Islamic group? In effect, we're allowing Islam to establish the rules of battle simply because it refuses to conform to a precise definition. It's not a country on a map, it doesn't have an identifiable government or uniformed army, so according to the left the numerous examples of its violence against us physically, and its hostility to our culture and institutions when allowed to live among us, are just that: the acts of individuals. That they are all rooted in the Islamic worldview is apparently just a coincidence. After all, how can you precisely delineate these terrorists from other Muslims? Until they commit actual violence, you can't. So I guess we'll just have to assume Islam is not an organized enemy right? /sarc
To echo the WWII analogy, you cannot eliminate enemies without taking out their support structures. The Nazis and imperial Japanese would never have been defeated if we didn't attack their factories and merchant transportation networks. We're never going to adequately meet this threat until we recognize that Islam itself is a giant support structure for jihad.