Yes as a practitioner of Wicca one believes in the Wiccan Rede and the rule of three, but many of us seem to have forgotten that not all pagans are Wiccan and not all witches are pagan. Therefore in chat and forums don't let that be your fall back reasoning as to why someone else shouldn't do it. If this is your reasoning then your logic is quickly dismissed in a single, "It doesn't apply to me," and wrong or not no one can really win a belief battle. So while I do not suggest giving up on telling others that you think what they are doing is morally wrong, I do suggest finding a more logic based less belief based reason. It would reflect better on the community as a whole and each of us personally if our fall back logic isn't faith based.
All this being said you have all the right in the world to believe as you may, about threefold, the rede, eastern karma, or western karma, but in a discussion belief, unless the other person is of similar beliefs, isn't the best fallback.