If you believe that nuking Mecca will “show” Muslims anything, then you don’t understand Islam.
The cult of Mecca — black stone, shrines, etc. — is considered idolatry by the Islamic State and other Salafists. It represents putting something before the worship of Allah, and is thus a form of shirk, or polytheism. The Islamic State has already promised to destroy the “idols” of Mecca.
If anyone were to nuke Mecca, they would be understood by devout Muslims to be carrying out the will of Allah. It would be seen as a punishment sent by Allah against those whose faith is less than pure, and a warning to Muslims everywhere.
The net effect would be to turn the survivors — which would be the vast majority of Muslims, even if the destruction occurred during the hajj — into Salafists. Islam, in effect, would be purified.
For those Muslims who consider themselves the true practitioners of Islam — the original form of it from the time of the Companions of the Prophet, al-salaf al-salih — the shrines of Mecca are just a racket set up by servants of Satan to divert Muslims from the true faith.
h/t Matt Bracken
There is only one way to deal with muslims. The answer is in in the Old Testament.