Do you mean protect yourself from revenge spells? Or to protect you from the karmatic trauma that can happen from doing them? The latter is impossible. You can protect yourself from them without harming others, but if you cast one it most likely will harm those around you as well as your intended target.
I would suggest doing protection spells for them instead of bringing them in into the circle. My boyfriend said why do you need revenge spells anyways. So Why would you risk doing revenge spells without protection if you want to get a friend for it?