It is a joke.
Terrorists can fly on domestic flights as well, therefore, if the threat is real no electronics should be allowed on US domestic flights either.
I read that the reason for the specific airports chosen was that terrorist sleeper security were in place to 'allow' pax through with devices that would otherwise be picked up. This justification was obviously untrue if there is a blanket ban. The ban is a tacit admission that the security at airports in insufficient.
Yet it is probable that the chance of a LiIon battery fire in the hold is higher than the chance of a terrorist bomb.
The word inept comes to mind.