This moral sense is often bigger and more powerful than us. Some people could call it psychological effect, others might term it differently but the fact remains that if we are doing something wrong, this moral sense would keep nagging us to the point that we would no longer be able to enjoy what we are doing and might eventually starting harming ourselves.
In order to protect ourselves from such negative consequences, its best to make a decision that is free of guilt. In this way, we can enjoy the fruits of our success and live a more happy life in general. This is really what is in our best interest though we might fail to see it at first.
It also pays to study the offer from an objective viewpoint. If someone else were offered this job: what would you suggest? Would you allow the person to take the job knowing that it actually means threatening the health of millions of people? I would equate such a behavior with being a vulture. Only a person with very low and base faculties might want to earn money at the cost of life and health of millions. Mill has rightly pointed out that if given a choice, no man would ever want to be in the place of an animal even if animals were generally happier with their existence than we are with ours. He writes: "Few human creatures would consent to be changed into any of the lower animals for a promise of the fullest allowance of a beast's pleasures; no intelligent human being would consent to be a fool, no instructed person would be an ignoramus, no person of feeling and conscience would be selfish and base, even though they should be persuaded...
Man can see himself being in control of his powers. He possesses higher faculties. He can think for himself, plan for his future, choose a course of direction and has a purpose in his life. All these are missing from an animal life and thus man chose to be a man. Now that he has become a man, why not actually give preference to things that make us a man such as our intelligence and our ability to be compassionate and conscientious.
Knowing that it was in my best interest to reject the offer, I turned it down and have never regretted it even once. I know that I could never enjoy success or money if I knew many people were actually bleeding because of this very success. If I knew that many were suffering in hospitals and living a poor unhealthy lives simply because I was selfishly pursuing money, that would make every single day of my life a nightmare for me. I am now happier and have a stronger sense of self-worth than I did before.
References
Richard Garrett, the GOLDEN RULE. Presented to the Starr King School for the Ministry, University of California at Berkeley April 12, 2002
Mill, John Stuart. Excerpts from "Utilitarianism" in Philosophical Problems, an annotated anthology by Laurence BonJour and Ann Baker, editors, Pearson education (2005)
Mill, p. 590
