Why talk about "Islamic terrorists"?

Chris Matthews asks:

Why does [Marco] Rubio want to have this as a clash of civilizations? I though that was what ISIS wanted, what al Qaeda wants, to have the Islamic world fight with the Western world! Why would he want what they want — to see the world in a religious struggle? Why say "Islamic"? Why don’t we say "terrorist"?

I'd resist any suggestion that we should speak only in vague terms about terrorism/terrorists and constantly avoid mentioning the ideological underpinnings of those who have built an international network that threatens civilization as we know it. There are many other terrorists around the world with a variety of agendas, but we rightly don't put as high a priority on stopping them because they lack the global ambitions of groups like ISIL and al Qaeda.

It isn't convincing to suggest that the terrorists aren't really Islamic because they're evil, and Islam itself isn't evil. Using the adjective "Islamic" to apply to terrorists is not saying that all (or even most) Muslims are (or even support) evil. If you believe that, then to be consistent, you should object to describing the Crusades as Christian, or the Holocaust as German, etc. Well I'm sorry, but you're just not going to get anywhere by trying to erase the parts of history that make you feel uncomfortable. Someone else, who's in the habit of speaking or writing more bluntly, will always be able to come along and point out the truth in a more compelling manner than you have. If you believe in your message about terrorism — whatever that message is — you should want to communicate it in clear language that describes reality with precision. Instead of objecting to those who use such language when it's disturbing, we should be fighting against those who have made the use of such disturbing language necessary.