Here are three ethical scenarios. Each assumes that the person making the decision is a Christian and understands pornography to be sinful.
You buy a foreclosed storage unit at auction, the rules of which prevented you from opening any boxes prior to purchasing the unit. While cleaning out the locker you bought, you discover a box full of pornography. You set the box aside along with several other items you plan to haul to the dump. Before you have the opportunity to throw anything away, a middle-aged man walks up to you and offers you $100 for the box of pornography. Do you sell it to him?
You invest heavily in the stock market. The pornographic industry is having a very good year, and you could profit greatly by buying stock in Playboy Magazine. Ethical considerations aside, Playboy would unquestionably be your best investment option. Do you buy the stock?
Your retirement savings are invested in mutual funds. This means a very tiny percentage of your holdings include stock in companies like Phillip Morris, Budweiser, and Playboy Magazine. You could opt for a specialty mutual fund that avoids morally objectionable companies, but your rate of return would be considerably less. Do you leave your investment where it is?
The Christian in the first scenario should throw away the porn. Selling it would promote sin, and would make you a party to that sin. While it would be nice to have $100, it would be much worse to dishonor God.
The Christian in the second scenario should not buy the stock in Playboy Magazine. As with the first scenario, buying part of such a company would promote sin and make the buyer a party to that sin. While the stock would otherwise be a good investment, pleasing God should be a higher priority.
The Christian in the third scenario should leave his or her investment where it is even though that mutual fund invests a small percentage of its holdings in objectionable companies. The key difference in this case is that there is no direct promotion or involvement in sin. Christians will never be completely able to avoid interaction with the sinful elements of their societies. However, they should avoid directly and deliberately profiting from sin.
Let’s go back to the first example. Say you bought the storage unit and found the porn. However, when the man walked up to you—rather than offering to buy the porn—the man offered to buy the entire unit from you for considerably more than you paid for it. Could you profit from the entire unit even though you knew one of the boxes contained porn? I would assume the man was not buying the unit for the porn and would sell it without overburdening my conscience (1 Cor 10:27)
Of course, the situations would be totally different if most of the boxes were filled with porn or the mutual fund in question specialized in objectionable stocks. However, while Christians must not be of the world, they are to live in the world. Sometimes this means they will indirectly profit from the sinfulness of their societies, but if Christians are to be not of the world, they should neither directly nor deliberately profit from sin.