Rightly Dividing the Word
The Bible is divided into several dispensations of time in which God deals with mankind in a certain manner. It can be understood in this way. What applied for Adam and Eve was a bit different when it came to setting up a nation of ex-slaves who were a bit barbaric. Harsh punish for crime is the best deterrent for crime as we have seen in other nations that have far less crime than we who are tolerant.
The governing body is given the exclusive right to pronounce a death penalty for criminal acts. The Bible says obey the law of the land.
In accepting the laws of God, and becoming God's people, Israel was attempting to become a holy nation before God while on earth. Notice that stoning or other forms of death penalty were not as much a punishment for crime but to put the SIN out of Israel, in this way, they maintained their holy status. This brought a much stiffer penalty for sin. Their penalty was suffered in this life. Man's penalty today in suffered in the next life or Hebrews 9:27 And as it is appointed unto men once to die, but after this the judgment: At any rate the Romans 6:23 says For the wages of sin is death; this death is separation from God for all time, that is forever in a place that burns with fire, forever. Stones are to be desired rather than this. People who did not know anything about this place have had experiences that demonstrated that this is a spiritual reality for the place of the spirits of men who have separated in death from their natural bodies.
The time in which the nation of Israel lived in this manner was the dispensation under the law. We are no longer under the law today. Thus the things in Leviticus 20; do not apply to us in this manner. They only serve to let us know about that these actions are sins before a Holy God.
AS time went along and Jesus Christ came on the scene, men were counseled to love. The foundation of the life of true Christians is first to love God, then their neighbor We are also counseled to love those who hate us. Not an easy task but one we can ask for wisdom on. In this we can find that acknowledging the truth of scripture, rather than emphasizing that love is only pleasantries will show love. The scripture says teach the people the difference between the holy and profane. The warning itself is mercy and love that can cause an honest heart to move out of the way of God's judgments. Further we are warned of trials, and chastisements, all these grow out of the love of God. Because it does not seem rosey, does not mean that it is not what a loving God means to say to mankind.