This is a logical fallacy. The Mosaic Law is not deleted, its fulfilled. Its purpose was to keep the nation of Israel prepared for the birth of Christ.
It does not mean that all good moral principles are now erased or something. Its still wrong to murder, to steal, to lie etc. It was wrong before the Mosaic Law, outside the Mosaic Law and also is wrong after the Mosaic Law.
However, many shadowy parts of the Mosaic Law do not continue for Christians. For example "eye for an eye", "you will not let a witch to live", "do not trim the sides of your head", "circumcise your boys" or "keep the Sabbath day".
Where there is no law there is no sin. Romans 4:15 Sin is the transgression of God's law 1 John 3:4 Romans 7:7
The only reason we know thou shalt not murder, or lie, or steal is a sin is because God said so. This is God's righteousness Psa 119:172 and we do not get to pick and choose what we deem is right or wrong as that is depending on our own righteousness and not God's.
The apostles always gave glory to God on His commandments, as should we.
James 2:10 For whoever shall keep the whole law, and yet stumble in one
point, he is guilty of all.
11 For He who said,
“Do not commit adultery,” also said, “Do not murder.”
Now if you do not commit adultery, but you do murder, you have become a transgressor of the law.
The He who said is God.
God both spoke and wrote His holy commandments, all glory goes to Him and we keep them through love and faith. 1 John 5:3 John 14:15, Exo 20:6 Rom 3:31 Rev 14:12
20
And God spoke all these words, saying:
2 “I
am the Lord your God, who brought you out of the land of Egypt, out of the house of [
a]bondage.
3 “You shall have no other gods before Me.
4 “You shall not make for yourself a carved image—any likeness
of anything that
is in heaven above, or that
is in the earth beneath, or that
is in the water under the earth; 5 you shall not bow down to them nor [
b]serve them. For I, the Lord your God,
am a jealous God, visiting[
c] the iniquity of the fathers upon the children to the third and fourth
generations of those who hate Me, 6 but showing mercy to thousands, to those who love Me and keep My commandments.
7 “You shall not take the name of the Lord your God in vain, for the Lord will not hold
him guiltless who takes His name in vain.
8 “Remember the Sabbath day, to keep it holy. 9 Six days you shall labor and do all your work, 10 but the seventh day
is the Sabbath of the Lord your God.
In it you shall do no work: you, nor your son, nor your daughter, nor your male servant, nor your female servant, nor your cattle, nor your stranger who
is within your gates. 11 For
in six days the Lord made the heavens and the earth, the sea, and all that
is in them, and rested the seventh day. Therefore the Lord blessed the Sabbath day and hallowed it.
12 “Honor your father and your mother, that your days may be long upon the land which the Lord your God is giving you.
13 “You shall not murder.
14 “You shall not commit adultery.
15 “You shall not steal.
16 “You shall not bear false witness against your neighbor.
17 “You shall not covet your neighbor’s house; you shall not covet your neighbor’s wife, nor his male servant, nor his female servant, nor his ox, nor his donkey, nor anything that
is your neighbor’s.”