 polytheism is only in seven sins which are the major sins adultery is one of them and slandering chaste women is also one of them. all of this is stated in the book of god almighty.
الشرك الا في سبع ذنوب، وهي الكبائر الزنا أحدها، وقذف المحصنات أيضا منها، منصوصا ذلك كله في كتاب الله عز وجل.