There is great debate about whether casting destructive spells (like curses, hexes, jinxes, crossings, etc.) is acceptable or whether it should be avoided at all costs. When it comes to this question I always defer to ethical questions to test the situation. I ask myself the following questions:
1) Would it be what I desire, or what is necessary? (does it come from my own feelings of vengeance or is it because the person needs to be stopped for the greater good of the community?)
2) Is it just in the eyes of God? (A reading is done to determine what the outcome would be if the spell were cast and whether it is just in the eyes of God or not. God is just and will not stand to see the innocent hurt or taken advantage of. Psalm 18, Psalm 35, Numbers 14...)
The notion of "harm none" when it comes to magic is a recent evolution that comes out of the modern religion of Wicca, and has very little to do with traditional witchcraft or magical practice. This "witches' rede" isn't adhered to within the tradition of Hoodoo. Hoodoo (Conjure) is instead based on African-American traditions that are the result of a melding of original African magical practices and a Protestant understanding of a just and vengeful God.