Arguments against a metaphorical bible
Hi everyone. Quick intro: I'm an atheist, long time lurker, and I've only recently (over the past year or so) begun to educate myself about atheism, and arguments against christianity. I didn't see any posts on this topic, and I'm too lazy to search though every forum. Sorry if this is in the wrong place, feel free to move it as needed.
So here's my question. Arguing against someone who interprets the Bible literally is easy. The Bible has plenty of contradictions and evil behavior in it. But what arguments are there against people who say the Bible is a metaphor? For example, you hit them with a verse that sounds bad, and to avoid a difficult explanation, they say that the verse is meant to be taken metaphoically. What is the best way to deal with that?
I go a souther, rural, baptist-affiliated school, so any help is greatly appreciated.