I think Blizzards response is appropriate and this matter need to shut down with a 'Thank you'. At first Blizzard's cookie cutter response was deplorable, but now your insistence. Let me tell you of a story regarding my WoW account. I have a clean PC with none other than the most annoying McAfee Internet Security and I run scan daily (scheduled). Yet, my WoW account got suspended one time. On researching, I found that somehow someone got hold of my email address - email address that I used on battle.net account. How? I am not sure - maybe the guild website I belong to? Maybe someone I know? Regardless, they tried to use that email address to change my password. Blizzard saw the activity suspicious (and rightfully so) and suspended the account. I talked to a person - went to my email account, and lo behold, I see a bunch of password change request that failed. After 24 hour, the account was un-suspended. So, my account DID NOT get hacked due to my PC, but because my email address was available somewhere OUTSIDE my PC.
Anyways there's two things that could have happened here. Either Blizzard got hacked and someone stole your account info from them, or whoever did it got some information from you that allowed them to access your account.
I think if Blizzard got compromised, they wouldn't just take your random account, and there would be a news thread by now. It's kind of absurd that you're refusing to even consider t hat you could be to blame, when the only other thing that could have happened is a massive compromise of Blizzards security. They are safe in assuming the problem is on your end, because it has to be.
So unless there's a news thread "lulzsec hacks Blizzard, steals one single inactive account to advertise for gold site" tomorrow, I don't think Blizzard did anything wrong.