Instead of me sharing my new post this week, I want direct your attention to J. D. Nyle's post about witches and why they would be considered evil by definition.
To be fair, I think the original definition of a witch is a woman who practiced magic in which the evil comes from magic being evil. It's probably more of a case that not all witches start of wanting to become evil, but since magic is evil, it naturally corrupts and turns them into evil witches.
In contrast to that, if we were to consider delving deeper into the nature of witches, I'd follow the line of reasoning that Nyle shows. I think the idea about the nature of a witch being complete opposite of that of a virtuous woman is a good one.
If you don't trust the hyperlinks, here's the link in plain text: http://neostrikershining.blogspot.com/2016/04/the-nature-of-witches.html
While you're at that blog site, check out his full novel for Neostriker: Shining