:Yes and no: for example, if reliable source A calls incident X "state terror", and uses argument Y to "prove it", then a separate reliable source B that supports argument Y might be used, even if it doesn't directly speak of "state terror". Likewise, if reliable source C criticizes argument Y, again with no mention of "state terror", they we can also use it. Also, even when there is no controversy per-se, you might want to use sources that provide supporting information, such as proving the existence of organizations or laws. Your perspective, I am afraid is a narrow one.

In other words, while the narrative should be around precisely source who do explicitly use the term, there are many instances where sources can, and probably need to, be used that do not explore the concept itself. Lastly, even when the phrase "state terror" is not used, but the article is clearly about the topic, it might be included. Rather than a blanket prohibition in the abstract, we should have a discussion on inclusion in the concrete for each instance.