Why can't Christians say that parts of the Old Testament don't apply??..

[DeistPaladin]

This is the argument that Christians use, when Atheists ask why people don't stone their neighbors for working on the Sabbath, and things like that. How do you counter arguments that these rules were for an earlier time? I mean, there are some old testament verses about people's animals falling into pits that certainly don't apply anymore.

I've had arguments with Christians (Folks I know in real life) about this and they usually reply with a) as you say, it was a different time with different standards for what was acceptable and not (i.e. enslaving fellow human beings) and b) since God is the source of what is right and wrong and acceptable, it's not our place to pass judgement on what he may have did or said in the Old Testament. I think both arguments are highly questionable and contemptible, but as Christians would say, that too is beside the point in the face of the prime mover, judge, jury and executioner.

And these are the same people who say we have a questionable source of moral guidance.