It is a big field of research. It is hard to say simply this is true or this is fabricated. It is a science of examining the old history and tradition. This science has its rules. I have many books and articles in how to conduct such research.This is my first field as I graduated from the Department of Muslim History of Al Azhar. The PhD holders in that department have the expertise in examining the details of Muslim History including Sira. In any case, it has nothing to do with the religion of Islam.