So basically religious morality is no different than atheist morality?
Difference is only a matter of whether all points of one correspond to all those of the other. Whether you think they do or not, then there is your answer.
Matthew 5:17 - Do not think that I came to destroy the Law or the Prophets. I did not come to destroy but to fulfill. For assuredly, I say to you, till heaven and earth pass away, one jot or one tittle will by no means pass from the law till all is fulfilled. Whoever therefore breaks one of the least of these commandments, and teaches men so, shall be called least in the kingdom of heaven; but whoever does and teaches them, he shall be called great in the kingdom of heaven.
Those are the words of Jesus himself saying that not one "jot or tittle" of the Old Testament shall pass away, and reminding people that the commandments of the Pentateuch remain in force.
Yes, "the Law and the Prophets" is a reference to the OT in general, but this says nothing about any specific laws. Matthew 7:12 addresses these:
So in everything, do to others what you would have them do to you, for this sums up the Law and the Prophets.
In other words, the intent of the law (and the OT in general) was still in force , but not the letter of the law. This is exactly as I said earlier. The rules can give way to maturity.