... so you aren't arguing the premise there (ie, that dirty bombs are inefficient for terrorists). So your argument is distressingly close to "terrorists would be ineffective if they did [this], so we should ban it to stop them making mistakes". I doubt you believe that, I'm just drawing your attention to the fact you have to attack the premise to get anywhere on this issue.

godelski is arguing that terrorists who can be convinced to try and use dirty bombs will be less effective than if they had chosen other, more damaging, options.