When you work for something that directly contradicts peaceful civil society you are basically saying the mass murder of today is ok because it allows you to assuage your guilt by giving to your local charity - its only effective if altruism is not your goal.

It still depends on the marginal contribution.

A janitor at the CIA in the 1960s is certainly working at an organization that is disrupting the peaceful Iranian society and turning it into a "death to America" one. But I would not agree that they're doing a net-negative for society because the janitor's marginal contribution towards that objective is 0.

It might not be the best thing the janitor could do to society (as compared to running a soup kitchen).