The Arabic word "Allah" is not a proper name. It is the generic word for God. I can be used for good or for bad. It corresponds to the Hebrew word "elohim" which can be used for the God who created the universe, or it can be used for the idols made by men. In English, we capitalize "God" when we talk of the Creator. We spell it with a small g when we talks of "other gods". The Bible uses it that way.
Our Bible (Old and New TEstaments) translated into Arabic uses the word "Allah" when it talks of God/Allah created the heavens and the earth.
If you do not understand the word, it can be difficult to talk with a Muslim and be understood. When Christians say "Allah is not God", it makes no sense to a Muslim. God is not God????
I agree the religion of Islam and the Koran is of a different spirit than the Holy Spirit of God. The average Muslim knows nothing of the Koran and illiteracy is rampant in the Muslim world. Many Muslims are willing to talk about Y'shua/Jesus and they feel favorable toward Him. They are suffering from a lack of understanding about God and His Messiah. WE need to meet that need with love and understanding by giving them the GOOD NEWS. We do not need to trash their religion. We need to use their understanding that a blood sacrifice is necessary for the cleansing of sins. WE need to point to Mohamed's own words about himself - he was totally unsure of where he fit and what God required of him. WE need to HELP THEM in the power of the Spirit to eat of the Tree of Life. ARguing facts true or false from the Tree of Knowledge will only deepen the rift. The Lord our Savior died to set them free! They are open to the gospel. Let's take advantage of that while the door is open - it will not be open long.