You seem to be biblically challenged here. While Moses was the writer of Leviticus, God was the Author. Moses was no more than a scribe taking dictation. The vast majority of Leviticus is direct quotes from God the Father as given to Moses.
To be sure you are certain that this is a direct quote I will include the entire portion of scripture in this post.
Leviticus 20:1 ¶ And the LORD spake unto Moses, saying,
(This means that everything after this is the quoted words of God)
Leviticus 20:2 Again, thou shalt say to the children of Israel, Whosoever he be of the children of Israel, or of the strangers that sojourn in Israel, that giveth any of his seed unto Molech; he shall surely be put to death: the people of the land shall stone him with stones.
3 And I will set my face against that man, and will cut him off from among his people; because he hath given of his seed unto Molech, to defile my sanctuary, and to profane my holy name.
4 And if the people of the land do any ways hide their eyes from the man, when he giveth of his seed unto Molech, and kill him not:
5 Then I will set my face against that man, and against his family, and will cut him off, and all that go a whoring after him, to commit whoredom with Molech, from among their people.
6 And the soul that turneth after such as have familiar spirits, and after wizards, to go a whoring after them, I will even set my face against that soul, and will cut him off from among his people.
7 Sanctify yourselves therefore, and be ye holy: for I am the LORD your God.
8 And ye shall keep my statutes, and do them: I am the LORD which sanctify you.
9 For every one that curseth his father or his mother shall be surely put to death: he hath cursed his father or his mother; his blood shall be upon him.
10 ¶ And the man that committeth adultery with another man’s wife, even he that committeth adultery with his neighbour’s wife, the adulterer and the adulteress shall surely be put to death.
11 And the man that lieth with his father’s wife hath uncovered his father’s nakedness: both of them shall surely be put to death; their blood shall be upon them.
12 And if a man lie with his daughter in law, both of them shall surely be put to death: they have wrought confusion; their blood shall be upon them.
13 If a man also lie with mankind, as he lieth with a woman, both of them have committed an abomination: they shall surely be put to death; their blood shall be upon them.
So you see it's one long quote where GOD says "They shall surely be put to death"
So I didn't give you Moses, I gave you the Word(s) of God. Now if you have an issue with what God says then take it up with Him.
And we've already discussed that Jesus and the Father are one. If the Father said it, Jesus said it.
You gave me the word of Moses.
"While Moses was the writer of Leviticus, God was the Author."
Matthew 19:8
Jesus replied, "Moses permitted you to divorce your wives because your hearts were hard. But it was not this way from the beginning.
Just as Moses gave you the divorce law out of the hardness in your heart, so to did he give you that little tidbit you wave to justify murder. Had God authorized you to kill folks Jesus would have said so and acknowledged that Moses was correct. He didn't! He didn't authorize the killing of witches anymore than he did the killing of Cain.