First: you might have more impact on the organization from the inside than from the outside (this is most relevant to people joining at a high/senior level). For example, Google seems to be making privacy far, far worse. Yet there are some people on the inside fighting to limit the privacy violations, which leads to decisions like banning GPS tracking in their contact tracing app[0]. Would the world be better or worse off if the only people working at Google were people who don't care at all about user privacy? I'm honestly not sure, but I can at least see an argument that it might be even worse off.
Second: you might get something from the organization that lets you do good that outweighs any harm you contribute to (this is more relevant to junior employees). Many employers provide something (training, future job opportunities, or a high enough income to open your own small business/non-profit). A thoughtful employee can go into a "negative impact" employer with eyes wide open and a plan to get something, and get out.
However, in either case, self awareness and a definite exit plan are _key_. As Drew writes, once you are working at a "negative impact" employer,
> Doublethink quickly steps in to protect your ego from the cognitive dissonance, and you take another little step towards becoming the person you once swore never to be.
The way to avoid that sort of conative dissonance is 1) know that you'll experience it and be on guard against it, and 2) know all along that you're there temporarily and should never get too comfortable. Even then, you should be realistic about how long you can maintain your personal values in face of a very different culture. For a junior employee, I'd say two, maybe three years should be the absolute limit before you get out.
[0]: https://www.reuters.com/article/us-health-coronavirus-usa-ap...