Why is witchcraft bad?

Because they aren't good but cast evil on the world because they find humans easy Target's.

Another response

The term "witchcraft" can mean a number of different things. People often speak of witchcraft when talking about evil magic, usually involving women who are not under the control of a husband, father or other male authority. When used this way, "witchcraft" is a figment of the imagination or a false accusation. People are afraid of strangers or of people who are strange, and so they accuse that person of witchcraft.

"Witchcraft" is also used as an insult when talking of religious traditions other than the major institutional religions, especially Christianity, Islam, and Judaism. These traditions, unfortunately, teach that there is only one "right" religion and all other religions are evil. Consequently, anyone who is not part of the major religion is considered evil and often believed to practice witchcraft.

Before Christianity, Islam and Judaism were widely practiced in Europe, the people in Europe practiced different varieties of nature-based religions. Today, people practicing those religions are called Neo-Pagan or Wiccan. They are condemned as evil by the major religions.