Comprehend
Res Ipsa Loquitur
If you read carefully, it says nothing of doing away with the old law. There has been change, but only changes that are after something has been fulfilled.
"Think not that I am come to destroy the law or the prophets. I am not come to destroy but to fulfil; 18 For verily I say unto you, one jot nor the tittle hath not passed away from the law, but in me it hath all been fulfilled. 19 And behold, I have given you the law and the commandments of my Father, that ye shall believe in me, and that ye shall repent of your sins, and come unto me with a broken heart and a contrite spirit. Behold, ye have the commandments before you, and the law is fulfilled. 20 Therefore come unto me and be ye saved; for verily I say unto you, that except ye shall keep my commandments, which I have commanded you at this time, ye shall in no case enter into the kingdom of heaven." -3 Nephi 12:17-20
God does not contradict himself. God only fulfills his own laws.
I love it when somebody tells me to read carefully. :sarcastic
If you don't see the difference between the OT law and NT law then I can't help you much.
Time of Chist:
1. Gentiles not allowed to hear the gospel or join church.
2. God changes law and allows Gentiles in.
Latter days:
1. Blacks not allowed to hold the priesthood.
2. God changes law and allows blacks the priesthood.
Could you explain how the two situations are different and why the first change is legitimate but the second one isn't?