Bad analogy. While I'm not into Christian beliefs this is a poorly thought out argument. They did a special on npr which went over the details of the encounter and it's validity. If I cared a little more I'd link it, but the summary comes down to this. Goliath wasn't even close to being in control of this fight. Goliath was, in fact, the underdog in this story, didn't even stand a chance at winning. when you math hammer the density of the rock where the battle is claimed to take place and the strength at which David (who was by no means scrawny) could throw the rock the power comes pretty close to that of a small caliber firearm. Slings wreak shit like it's their job. Do the research and you'll see how silly your claim is.