always only destroy pre-Islamic treasures! Why don’t they destroy Islamic ones? Why is that?!
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For the same reason that archeology is illegal in Saudi... Any such Islamic site dating after Mohammed is “holy”; any site dated to the time of Mohammed (or before) has the possibility of contradicting Mohammed, and thus is anathema and must be destroyed.
Any site not related to Islam is also anathema and must be destroyed.
Yes, I think, you are correct for strictly non-Islamic or non-Moslem related historical sites. As well as those related to Mohammad, himself, before he became a believer in Allah & Islam himself.
Additionally, any site dating to (or before) Mohammad has the possibility of leading to 'worshiping' Mohammad, himself, or others, which would be considered Polytheism.
In Islam, Mohammad is only viewed as The final prophet, or more accurately The final Messenger ("rasul allah" literally meaning "messenger of allah" in Arabic). But Mohammad, himself, as important as he was in spreading Islam, is/was considered a mere mortal man nonetheless, who can't be worshiped.
SC -- In relation to your comment in post #43, both Spring of Zamzam & the Kaaba are considered much holier than Mohammad, because they date back to the time of Abraham & Ishmael, for moslems, therefore directly represent Allah.
Remember, Moslems view Islam as an Abrahamic religion. The difference there between Jews & Moslems is that of Abraham's son Isaac vs Isaac's half brother Ishmael (both sharing the same father being Abraham). Don't want to start a debate regarding that. Only to state what Moslems believe; whether it is true or not is something for Moslems & Jews to sort out. Since I am neither Jewish nor Moslem.
Also, my understanding is that many moslems actually perform mandatory ablutions before prayers with the water from Zamzam Spring. The water is also believed to have medicinal qualities, so many pilgrims take liters of Zamzam water back home with them to drink from time to time, especially when ill.