Why was the Hun messenger killed in the classical Chinese "Grasping the knife at the bedside to kill people"?

One is a guilty conscience, and the other is a concern.

Cao Cao installed a bodyguard to prevaricate Cui Yan, but he didn't expect the Xiongnu messenger to have a unique vision and saw him at once, which made Cao Cao feel very uneasy.

First, they are afraid that it will spread to outsiders to make jokes. After returning to China, their emissaries will definitely explain to Khan, which is extremely unfavorable to them.

If the Huns knew that Cao Cao did it, they might go to war and add tar to the already unstable China. Especially Cao Cao. So he had to kill this man.

Killing the Huns' emissary just didn't want the Huns to know that China was weak at the end of the Eastern Han Dynasty, otherwise foreigners would attack.