No brainer: join to move the needle in a sensible direction.
-Nietzsche
I believe there is a notable and recent case of how this actually plays out. What was it? Towden? Mowden?
See also Schindler's List for an example of how a contractor of the enemy can undermine it.
I have not seen Schindler's List, but he also acted against and outside of the organization, rather than "move the needle," yes?
Schindler saved a thousand people through some pretty ballsy actions. But for scale, the battles of Stalingrad, Leningrad, and Moscow each had total casualty rates for both sides of 1-2 million people apiece.
Also, there is some indication that Schindler sabotaged the bomb parts he made so he saved more people than is immediately obvious.
Sensible in that place means catching terrorists.
It's easier to justify injustices if you can rationalise it by saying you are saving lives.