I think that is one of many salient differences between the scenarios.
My thought is: if one argument is good and another is bad, clearly the reason for the difference does not exist within the properties they share. It must exist where the arguments are different, or more likely in this case (as what the poster said and what I said are so similar), in the outside world of facts and understanding.
But if the shape of the argument allows for things that may successfully convince you, then clearly that information is not enough to dismiss it outright. It should be the start of a dialog with the parent comment.
Now, for something completely different:
If, for some reason, you want to actually engage _me_ on this particular policy issue, angle your thought at this: my understanding is that it's 2014, and if you want to regulate the information people share or sell over the internet you've accepted a challenge I do not envy.
I would be particularly skeptical you could do this without building a comprehensive computer spying system and perhaps outlawing crypto (it's been tried), as you're trying to read communications of highly security-conscious people.
As for if Mitnick is a good person (or similar things under discussion here), I have not met him.