A - Thanks for the question. I think this is a good thing to ask -should I patronize a business or buy a product of a company that is promoting something that I differ with morally? The answer is somewhat nuanced.
Second, you should always follow your conscience.
Third, you would not be sinning if you continued to shop at such places or buy such products.
Why is this?
The principles are similar to a question I answered recently about paying taxes.
We can never directly support intrinsically evil actions. Abortion, same-sex marriage, cloning, fetal stem cell research, euthanasia are some of the actions a Catholic cannot support morally. Yet, there are times it seems we get "tangled up" in these issues despite our best efforts. This is where the principle of material vs. formal cooperation with evil comes in handy. No matter how hard you might try, there are situations were good an evil are mixed up and sometimes we get caught being complicit in an evil act.
When we "cooperate" in an evil act our cooperation can be either "material" (meaning well-removed from it) or "formal" (close to the evil act). So, if you went shopping at a store because they had the best prices in town on books and while you were checking out you noticed that they also sell pornography, you could still licitly still shop at the store, if you don't intend to support the selling of porn. But, you are still in material support of the evil. A good rule to follow is that while material cooperation may be licit, we want to be as far-removed from formal cooperation as possible. So, if there is another option of shopping somewhere with similar prices and selection, which doesn't sell porn, we might shop there instead. Remote cooperation is licit because we don't intend to cooperate in the evil act and if we did intend to coooperate with evil it is no longer a licit act.
If the evil act is not intended by someone and the person is sufficiently remote from the act, then they are not complicit with it. This is called remote material cooperation. Things that might cause an act to be remote include (not in order and an incomplete list):
- Time between the complicit act(s) - in some cases, time between events can cause distance. But, time is not a cure-all. For instance, using research gained from the Nazi death camps is still immoral.
- Steps separating the complicit act(s) - For instance. If you buy a piece of clothing that was originally made in a child-labor sweatshop from another part of the world, then you are many steps from the original evil (sweatshops using child labor). If we intended to buy it because we support sweatshops, then we would be complicit.
- On-going or one-time (or completed) complicit act(s) - The US supporting slavery is an example. We no longer allow it, but how are we now responsible as a people for once doing so? On the other hand, the sex-trade is still an on-going problem. We cannot participate in such evil.
- Severity of the complicit act(s) - For instance, abortion. The act is an indescribably evil in and of itself. We cannot cooperate in acts that formally support such evil. On the other hand, there are lesser evils where it is not quite as clear.
- Nature and Immediacy of the Goods - The most common example is a custodian at a hospital that performs abortions. As long as the person does not formally cooperate in them and disapproves of them, he is not complicit in them - if he is dependent on the job for his livelihood. If he is able to get a job elsewhere, then his cooperation could be formal and not material.
The less remote the cooperation, the more we should seek to do something different. Once it is no longer remote from an evil, we ought never participate.
I hope this helps.