What are the Ethical Standards for Witchcraft?

Witchcraft itself doesn't have any universal ethical standard that all Witches MUST adhere to. Witchcraft is not an organized grouping and as such it has no universal standard set by any authoritative figures. Unless practicing within a group or Coven, Witches adhere to individually set ethics. Usually these ethics abide by common sense...don't kill, don't intentionally hurt for the purposes of amusement, etc. but some actions may seem contradictory to common sense unless you actually understand the concept behind these actions.

Take for example, the simple "Curse". To most, modern Witches may avoid using curses. Perhaps to avoid confirming any bias set against Witches in that they use curses to hurt others. On the contrary, curse can be used to protect others. For example, someone is continually being abused by a family member or loved one. To place a curse on this abuser could potentially stop him/her from further causing harm to those people, thus being protective. 

Now, if you are a Wiccan who is also a Witch, you may adhere to the ethic "The Wiccan Rede" (alongside whatever personal ethic you adhere to). The Rede, an EIGHT WORD guideline that states "An it harm none, do as thou will". Essentially, in a tiny nutshell, it says if what you want to do doesn't harm anything, then go ahead...though it says absolutely NOTHING about what should happen if you should harm. Harm is a personal choice. You choose whether or not you want to harm, but you also choose to accept the consequences of your actions should you DO choose to harm. This is why it's so vital that you think long and hard about what you want to do, if it will in some way cause harm, and whether or not that harm is justified for a greater good. You also have to think if you can accept the consequences of your actions. Can you handle what comes of what you do?

This is essentially what I mean by common sense. Will what you want to do mesh with your personality and what you would normally do?

Witches are not the sort to wave their hand and do what they want. Just because they possess a knowledge and practice what most don't understand doesn't mean they literally do whatever they want. Most have that personal ethic they abide by. I personally do not take curses lightly. I believe they are only to be used if all other means have been exhausted (and essentially, this concept also goes for spells as well). Just because I can curse someone I dislike greatly, doesn't mean I should. Everyone is entitled to their opinion, just because I don't like their opinion doesn't mean I can negate his free will to have that opinion; just because someone hit my car in the parking lot and caused a big dent doesn't mean I get to curse him for the incident. My ethic is to not believe my practice is my toy; that I need to be responsible for what I do therefore I need to be vigilant and cautious before casting. It's not a difficult concept, and living with an ethic can stop you from doing something you may regret in the future.