Christ did not abolish God's laws for human behavior
Many brothers think, erroneously, that God's laws for human behavior were abolished by Christ. Those laws abolished were the ritual laws. This was very clearly said by Jesus Christ himself, in Mt 5:17-19.
17 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, Till heaven and Earth pass, one jot or one tittle shall in no wise pass from the law, till all be fulfilled. 19 Whosoever therefore shall break one of these least commandments, and shall teach men so, he shall be called the least in the kingdom of heaven, but whosoever shall do and teach them, the same shall be called great in the kingdom of heaven. (Mt 5:17-19)
If the hypothesis that God's laws for human behavior were abolished when Jesus was nailed to the cross was true, then we would have to come to the conclusion that, at least up to Jesus' death they were valid. In this case, if Jesus would have wanted to abolish the law, or speak against it, he would have never done it before the crucifixion, because that would have been to fail, to sin against God's law and he could not have saved us.
If Jesus would have wanted to speak against the law or declare it null, he would have waited until his resurrection and then do it legally, without failing in anything. If Jesus would have talked against the law while it was still valid, he could not have saved us, because he would have sinned by despising the law, as we see in Hebrews 10:28.
He that despised Moses' law died without mercy under two or three witnesses (Heb 10:28)
To say it more clearly, if Jesus indeed would have abolished the law, he would not have done it before his death, but after his resurrection. However, we see that this kind of verses where apparently Christ talks about abolishing the law was never discussed by him after his resurrection, which is precisely when he could have done it, and done it legally.
It is the twisting of his words during his Earthly life that the challengers of the validity of the laws of God for the human behavior, have always held on to. But all these attacks and all these arguments based on words prior to his crucifixion, fall from their own base in this last reasoning, because Jesus would never say or do any thing against God's laws before his crucifixion, but after his resurrection. However, after his resurrection he never ever did so.