The aggressive Muslims (not extreme) love to contend with Christians on the validity of the Bible. Highly motivated by one of their heroes, the late Ahmed Deedat, they've challenged the Bible with Christians around the globe, particularly of the Western countries.
My soundbite to this challenge is simply:
Since the Bible predates Quran, it is better to admit humility, than to say if God's word is questionable then it is not God's word. It is better to seek the will of God patiently, than to make sense with new movement and betray the old.