Not at all. Just because something is metaphorical doesn't mean it doesn't have rules. Mathematics is a metaphor for the physical world, and yet is the backbone of all empirical reasoning.

The problem comes when people don't follow their own metaphorical rules - which is what I believe Matthew starts doing when he raises questions about what it even means to say that Jesus rose from the dead.

Zero is to one as black is to white as dark is to...what do you think? Obviously the answer is "light". If I tried to tell you otherwise, you'd know I was playing shenanigans - which is essentially what I think Matthew ends up doing in order to "save" Christianity (I am an atheist, by the way). But it's totally possible to talk in metaphors and also be totally empirical and intellectually honest.

Also, please see my response to Ben's response - which is where I think conversations like these really need to head.