I've been wondering that for awhile myself. However, when they (Bible literalists) say it is the word of God they could also be speaking in a less literal sense in that it was Divinely inspired.
While that sounds pretty reasonable, the point you have adressed toward those who believe it is absolutely the word of God and not of humans is a good one; and I'd like to debate them as well from a theistic standpoint.
Wanna feel God? Step onto the wrestling mat and you'd be crazy to deny the uplifting spirit.