The Quran rejects forcing anyone to join Islam.  God says in the Quran:

“Say, ‘The truth is from your Lord,’ let him who will, believe and let him who will, reject, it.  For the wrongdoers We have prepared a Fire whose (smoke and flames are) like the wall and roof of a tent, will hem them in: if they implore relief they will be granted water like molten brass that will scald their faces.  How dreadful the drink!  How uncomfortable a couch to recline on!” (Quran 18:29)