People call The Iliad a myth because it shows clear elements of the genre of mythology. The literary structure of the narrative itself lends to the idea that it is mythos.
Since you made this question as a parody of a Christian's...The Bible is made up of many different types of literature. To put any one label on it, like "myth," shows that you don't understand what the Bible actually is. There may be certain books that are myths, but there are just as many that are not, like the Gospels. The Gospels, for example, have the literary structure and use many features of Greco-Roman biography, and have very few characteristics of mythos.
Sorry to spoil the fun. Enjoy the pats on the back from your atheist colleagues.