It seems to me that he deliberately fails to define it, because "fundamentalist" has become such a hot-button code word for "religious jerk." Do you know anyone who defines themself as a fundamentalist? I don't. I define myself as a biblical Christian, who attends an Episcopal church because I grew up there and am comfortable with the liturgy and the music. But, if you cross-examined me in detail on my beliefs, many would describe me as "fundamentalist". To a lot of people, if you believe that the bible means what it says, you are a "fundamentalist".
It seems to me that Warren is trying to bypass that hot-button stereotype, and I'm not sure that's a bad thing.
I do. In fact I define myself as a White-Anglo-Saxon-Protestant-Right-Wing-Conservative Fundamentalist-Evangelical-Christian-Jesus-Freak. And if that doesn't offend just about everyone, then I'm sorry. I tried.