Add: Retribution.
Punishment is for those who commit a wrong or crime, to encourage rehabilitation and also to grant socity it's due vis a vis the wrongdoer or criminal.
Retribution is meant to send a powerful message to others that strong medicine comes to those who would consider a monstrous act.
IMO, Justice for an act commited is not enough to deter fanatics. Only the certain knowledge that fanatical acts will bring retribution to the fanatics themselves, their organizations, their extended families, and their entire people will possibly dissuade them. This requires more than punnishment, but knowledge that retribution will be swift and terrible.
I agree with your post and its intent. To make doing what they did result in the horrible death of their kith and kin. I don't think these people are sane enough to care what happens to them, their families or their country. The only caution I have about retribution is that we may run out of ammunition. But, having said that, I am in favor of "Nukeing" Mecca, if the Muslims don't turn in Bin Laden and Saddam Heussein (who I believe had a part in 9/11).