In another thread a person asked the question whether or not it is sinful to shop at Protestant churches and Salvation Army thrift stores. The answer was that a charitable donation wasn’t acceptable, but the purchasing of products or services was. This caused another question to arise: Is it sinful for a Catholic to purchase products or services from an immoral business?
That would depend on what the business was and what the products were that were being purchased. If the products were to be used for an immoral purpose (e.g., artificial contraception), or if the business itself were so immoral (e.g., pornography) that one would do better to find even a morally neutral product elsewhere or do without it than to give the business one’s money, then yes, a Catholic should avoid doing business with such a company. But without a specific example to consider, that is all I can say on the question.