I like the metaphor of a tour guide.  But it does allow for one erroneous viewpoint.  It's been a prevalent viewpoint through the modern era of the past two hundred years or more. 

This error is that if someone can't see the truth of Scripture, the truth of Jesus Christ and the truth of God the Father who created everything, that person is either stupid or evil.

This flawed viewpoint has contributed much to abuse in almost any religious system you care to study for very long.  It is not limited to Christian history. 

The tour guide metaphor as Bell describes it here fails to take into account the fact that a tour guide is not pointing out things in a vacuum.  The tour guide would be pointing out things that already have explanations, already have myths and explanations and all sorts of things.  It's not that people who haven't heard the Gospel haven't come up with explanations for anything, after all!  If that were the case, the work of missionary/tour guides would be so much easier. 

The truth of the matter is that everyone has their explanations, and they're pretty happy with them overall.  They've been refined over the life of a community and an individual until they're very, very convincing.  So the tour guide's job is to go into a place and offer an alternate, competing explanation.  This is much harder than walking into a vacuum and providing an explanation for things that nobody had ever bothered to explain before!