This is a stark example of how narrow-minded today's Muslims can be. Using the word Allah should be a matter of honor for them, and a basis of unity among mankind.
Does the Qur'an say anywhere that Allah is the deity of Muslims alone? Rather, the Book is replete with the contrary.
From A to Z in the Book, Allah is the Sustainer of the Worlds, Nourisher of all humanity. It should never have been an issue of contention ever.
Still, the Christians have taken the right stand: The word Allah antedates the advent of the exalted Prophet Muhammad in 610 CE. The Christians, Jews, Coptics (and idol worshipers) in the Arab world called their God as Allah. Allah being "an exclusive property" of Muslims is as foolish an assertion as can be.
The Arabic Bible has been using the term for centuries. Muslims should have enough sense to know that even Prophet Muhammad (S) was sent to all mankind. He is not ours alone, but of all those who would accept him.
Where does the Qur'an ordain flogging for drinking alcohol? Where does it ordain people to destroy temples or protest against them?
How long will it take the Muslims to come out of Jaahiliyah (the Age of Ignorance)?
Primarily, it is the Mullah who keeps pulling them back to Jaahiliyah. The Muslim masses, well, they behave no better than a herd of sheep.
Due references from the Qur'an:
1:1, 2:251, 10:31, 22:40, 41:30, 46:13, 114:1 and many more.