You have to distinquish between the law of conscience which we are all under, the Adamic and Noahic Gen 9(1-17) law which applied to the whole earth, and the Mosaic Covenant that only Israel was under (Deut. 4:7-8; Ps. 147:19-20; Mal. 4:4).
The Mosaic covenant includes several parts. It includes moral law, which is instructive to us all about what it means to love others and things you shouldn't do. In other words, nothing in the mosaic law binds us, but to the extent that it illuminates the Noahic law, then it's instructive.
The Mosaic law includes civil law which only applied to Israel. It included ceremonial and Kosher laws which only applied to Israel. The kosher laws were to separate Israel from other nations. (Lev. 11:44-45; Deut. 7:6; 14:1-2)
Gentiles had no dietary restrictions except not to eat an animal with the blood still in it.
The Mosaic Law vs the Law of Christ
You can apply your the law of conscience to your witch problem. You are required to love the witch as she/he is a special creation of God as are we all. But practicing and consulting witchcraft is a sin against God. Whether it's a criminal violation is up to the society of man, who God gave dominion over the earth. In Israel it was a criminal violation and the death penalty was specifically authorized and commanded by God to Israel.
Once again cleverly avoiding trying to address the moral status of the laws of Genesis. I just re-read Gen 9(1-17) to find out what what God doesn't forbid to us gentiles, and am happy to report that we can covet our mothers, commit adultery, and worship false idols, all without sin.
You are required to love the witch as she/he is a special creation of God as are we all.
Just as was the case with Torquemada.