Simply put, you follow a different Allah than us.
Maybe the Quran says you follow the same God of the Prophets and of Israel, but he is far different than our God. We accept out God as the God of the Prophets and of Israel. We both can't lay such a claim cause there's some major differences between our faith's perceptions of who God is.
In my other post we're talking about some major differences, love is one.