Do people really have a duty to fix every wrong in the world? He reported it to the project head, and resigned. He ensured he wasn't a part of the situation.

I don't think you have to be a full saint to fulfil your moral obligations. He ensured he wasn't implicitly participating and reported it to someone who had a responsibility to investigate/do something about it. That is a reasonable amount of effort to rectify the situation in my opinion.

> Yes I know it’s not all that rare, BECAUSE people can’t be bothered to blow the whistle.

The person you are responding to did "blow the whistle". They reported it to the project head. That is blowing the whistle.