You can read what Ratzinger said HERE. See page 2 para 2.
He claims, like his apologists, that he was not seeking to cause offence, yet it is difficult to see how he could expect any other reaction given the thesis he is advancing and the manner in which he presents it. As a scholar he can have been in no doubt about the possible interpretation of his words or the impact they might have upon the Umma, especially in the current theopolitical climate! He has claimed that he was merely citing the Emperor Paleologus, and indeed he kept doing so, but the problem he has is that he is arguing about forced conversion, religion and violence and his selective interpretation of selected texts within Qu'ran. All too familiar I'm afraid. He appears to misinterpret the topos of ji'had!