I say:
This may be addressed from several angles.

First:
The doctrines he has mentioned reflect the extent of his knowledge and his familiarity with particular men and their views. Most of what he knows consists of accounts that have reached him of the views of certain groups of speculative theologians and philosophers, such as groups among the Muʿtazilites and Rāfidites, groups of Muslim philosophers, and groups among the later followers of al-Ashʿarī. He then treats these people as the majority of rational thinkers whose views carry weight.

As for the positions of the adherents of other religions—the Jews and their various sects, and the Christians and their various denominations—he is among those least acquainted with them, as his books demonstrate, even though the People of the Book are closer to the Muslims than the polytheists