Debunking atheists on christians not following the law of moses

[JuliaL]

So if the big guy in the blue sky changed his mind about enforcing the OT rules, shouldn't NT people be concerned that he's going to pull the same stunt again, not to their benefit? Seems to me scriptural instructions on what is still actionable are vague enough that this guy can't be trusted not to weasel in the future. If the law is no longer active, then he is pretty slippery about changing the terms of a covenant after signing.
He can do that given his day job of ruler of the universe but that's no help to me or the Christian who's fully vested.