Contradictions in the bible

Dan Barker once asked an xian what they would count as a contradiction in the bible. They said that it would be something like one gopel saying jebus was cricified on a tuesday and the other saying he was crucified on a Friday. Now when xians want concrete examples of contradicions like that how can us atheists possible argue our case? Xians seem to think that if they can find a way to reconcile the contradictions we produce it somehow makes them go away but why? Simply saying one was using metaphoriacal language, or that they are refering to different times or just because one gospel doesn't mention it doesn't mean it contradicts with the gospel that does is a complete cop out.

Take the two genealogies, now they clearly contradict each other and yet xians will claim that one is for marys side of the family and the other is for josephs. As if we are going to accept that.