Think for yourself. The human ability for group-think is terrifying if you really consider it. I think a positive thing that one can do in general is try very hard to avoiding getting sucked into arbitrary groups and "clubs".. We evolved a very powerful capacity to identify with others and form loosely structured groups around shared notions and values. They form so swiftly and effectively that I would argue that mob-like amoral behaviour is something we participate in instinctively, like chimps. This makes it difficult for us to abstain from. But it can be seen that individuals who are bound together and begin acting in tandem can do things that the individuals would not do alone. Its the seceding of control up the hierarchy that we evolved within and the desire for conformity that bind groups and convince its members that otherwise repugnant behaviour is okay.
The moral thing to do would be to either actively resist the immoral action or, in a more passive manner, avoid participating.
