Funnycn
Its-beezy
Do I believe it is possible that someone can avada kedavra a b***h? No.
But if you look into some wicca practices and compare them to the idea that (and I forget the name for this so please forgive me) if you bring a certain energy - you can expect results similar to that energy, or that through believing something of a certain energy can happen, that it will, then maybe.
Like the practice of writing something (such as a goal) on a candle and letting it burn all day. That candle will be on your mind, making you more determined to meet that goal. That is possible. It can't really be proven that it was the practice that helped you meet that goal however it is a source of determination
So to a degree, some form of witchcraft does exist, is what you're saying?
For the sake of contrast, I will also give my opinion on this conclusion.
The idea of semantics, the power of suggestion, the placebo effect, and motivational drive are all well documented phenomena which can explain what you call witchcraft.
What need does the rest of the community have in using the word witchcraft when words exist that have much more explanatory power?