"An atheist, anti-religious, Jew who was born of a Jewish mother would still be considered halakhically Jewish, and therefore accepted as such by his fellow Jews." - Page 11
“In a modern context there is considerable resistance among traditional Jews to the characterization of Judaism as a religion, for this seems to imply a belittling of its status. They do not consider Judaism of a class with Christianity, Islam, or Buddhism, it is unique and in a category of its own as recording the divinely revealed teaching mediated through God’s Covenant with Israel.” page 5
The Jews: Their Religious Beliefs & Practices (1999 Edition)
http://books.google.com/books?id=y3--5jTheDUC&pg=PA128&lpg=PA128#v=onepage&q&f=false
Author: Orthodox Jew Alan Unterman
http://pipl.com/directory/people/Alan/Unterman