They're afraid they might turn out to be false. That's the only way to generate unity. Such leaders draw their power from the fear they are able to whip up by painting external threats. It is how some leaders stay on their throne. Truth gets trampled under the feet of pragmatism.
Truth becomes whatever is useful.
And it is useful to have an enemy to unite the people. As long as it keeps the troops fearful and under my command. I dislike sensationalism. It's all the same. The trouble is, many who read the super market tabloids suspect they are invented stories.