Paul N. Anderson explains how the two really can go together:
Think of it! What would happen if the National Geographic Channel ran a special on a recently discovered gospel text from the late first century, which was different from the Synoptics but also developed an alternative rendering of Jesus and his ministry? If the third-century Gospel of Judas created a stir, with virtually no historical-Jesus tradition within it, imagine what sort of a ruckus would emerge if John were taken seriously as an independent Jesus tradition, differing from the Markan gospels with at least some knowing intentionality. That’s what I believe will happen if the Fourth Gospel’s historical features come out from being eclipsed by its theological ones.