First let me start off by asking the burning question: why the hell would you want to mouth off to someone who can destroy you in a whim?

To answer this question I think we should explore Cobra Commander's roots acording to Cobra-La's leader Golobulus. When a brilliant young nobleman was brought to his attention Golobulus decided that this is the one that he would send out into the world. The reason for this deed was simple. Golobulus wanted someone who he could send out into the world to raise a mighty army and destroy the world. Golobulus had the impression that Cobra Commander was his hope to conquer the world and take back what, he felt, rightfully belonged to Cobra-La and eliminate the so-called civility of the human race.

After many failed attempts to conquer the world Golobulus implanted the idea to create Serpentor into the head of another brilliant man Cobra scientist Dr Mindbender. Once this idea was discovered Cobra Commander's troops abandoned him iin favour of joining with Serpentor and Golobulus for world domination.

What Was Golobulus Planning?

In order to reduce mankind to a level of Cobra-La's idea of the perfect society they first must launch dozens of inmature pods into the earth's outer atmosphere. What's the purpose of this madness? To send millions of gene altering spores into the earth's atmosphere and turning the human race into unintellegent life forms.
In order to accomplish this task Cobra-La must be in posession of the only thing that can heat up the pods to the right temprature and that is the Joe's B.E.T. or Broadcast Energy Transmiter.

Your Plan Is Laughable

Cobra Commander, being too mouthy for his own good, suddenly mouths off to Golobulus telling him that he doesn't have the B.E.T. or even know where it is. The final straw is when he referred to Golobulus's plan as" laughable." (Uh you'd better keep your mouth shut Commander because I don't think Golobulus is done with you yet.)

Crime and Punishment

Cobra Commander had been convicted of the most heinous crime in Cobra-La's society. Failiure. As his punishment he was exposed to the very same mutant spores that kept his face hidden for centuries.

What's The Lesson To Be Learned?

2 lessons can be learned from Cobra Commander's execution. A) It's not wise to mouth off to somebody who can destroy you in a whim, and B) Mouthing off to somebody who can destroy you in a whim can have consequences that even you don't want to know about.