Yeah, I agree with pettygrudger - most don't really know the bible. The have no idea for instance when events occured as described in the bible in relation to things not described. eg. what else was happening when Daniel was written, when the isrealites were supposed to be captives in Egypt.
Their knowledge is shakey and restricted to 'soundbite' scriptures. I think this is why they will not have a good discussion with anyone who knows it and isn't one of them.