Question: A Buddhist friend encountered a cult-like group that rides upon but misrepresents Buddhism. He wonders if it is alright to volunteer in helping them to promote some general good values. Will this create any negative karma?
Answer: He should avoid helping them entirely, in the name of their warped belief system. Here are 2 reasons why –  It lends support to such deviant groups, helping them to grow generally, even if not specifically in terms of spreading their wrong teachings. When others who are less wise and discerning are drawn in as a direct or indirect result of his efforts, they will be spiritually poisoned eventually. Thus, it is better to focus help orthodox Buddhist groups grow, because if even Buddhists do not do so, who would?
 The fact that he does not realise that mentioned in  means he himself is probably not wise and discerning enough, and is likely to personally be spiritually poisoned eventually too, through continual association with the group. Usually, we say negative karma is created only when there is intentional action. Since now that he knows the negative potential of helping a cult, especially after this is shared with him, there will definitely be negative karma created if he decides to help and actually does so.