David Hume (18thC Scottish Philosopher) pointed out that miracles were claimed for all kinds of religions, but a miracle is something occurring through the intervention of an all-powerful etc, God.
If miracles are claimed for Christianity and for Islam and again for Hinduism, how can it be possible that each one has an all powerful God? That's a contradiction in terms.
Once the miracles are undermined the religions are undermined because their central idea is based on miraculous events (Virgin Birth; Hindu Gods drinking milk).
That's the view nowadays; that God is the same God wherever his worshippers are, but if you look hard at the history of Roman catholic miracles, many of them were supposedly wrought by God against the "Mohammadans", as muslims were once called. On the other side, Allah has supposedly done the same at certain times against the Christians. All of this during the crusades.
However, if we now say it's a mistake and God is God whatever his name, it means the Vatican (and others) would have to revise the idea and that weakens their credibility. For why should you believe what the Vatican (or any other group) says in matters Godly when they have to admit that there was no 'miracle' after all (this time)?
as we all know... history is written down according with the best interest of that times power.. even when we check now.. There is more europeans as scientists during the industrial revolution and then on.. because they were the one who ruled the world.. and do you think they were the only branics and all other knew nothing about inventions.. if we take an example right now.. we all know why US invade Iraq.. and then it changed to Iraqi Freedom.. and think... after 10 or 20 years what is going to come up in the note books of high school kids.. So existing power can always change the facts for the generations to come... right?