This is a business, or this is as a favor? Are the items specific to this event? Is there some reason that your making these items would be taken as endorsement of disordered behaviors between persons of the same sex rather than evidence that when it comes to clothing you deem acceptable, you will sell clothing to anyone without requiring the buyer to pass a morality test? For instance, are they asking you to do the sewing for free in return for recognizing you as a sponsor of the event?
For instance, let us say you make custom shorts as a business. Someone orders a certain number of customs shorts, something you’d usually make without any knowledge of where they were going, but with the rainbows all over them, you comment that those are unusual and the customer mentions in passing where the items are going to be worn. In that case, the morally-neutral item doesn’t magically become immoral. If it was OK to make if you did not know where it would be worn or who would be wearing it, it is still OK to make it if you find you’re making it for someone espousing some kind of immorality.
If, on the other hand, you’re being asked to make something that is morally repugnant quite apart from where it is going to be worn, because of the cut or what it depicts, such that you are being asked to make something you wouldn’t make for anybody, that is something else again.
I could not say what your situation is with regards to the legality of the matter, either. Keep in mind that when the government makes it illegal for you to refuse to do something, you are obviously not giving tacit approval by agreeing to do it as you would in a situation where you are free to back out if you are uncomfortable. For instance, if the President of a country were to choose to do something legal but immoral, the political people who chose to get themselves into a photo-op with him when he publicized it would be fairly seen as endorsing the act. His security detail, career government specialists in protecting public figures, would not. No one makes any assumptions about the political beliefs of a US President’s Secret Service detail, even though they are the only ones surrounding him who would literally take a bullet for him.
Finally, even participating in an event has some subtleties to it. For instance, there is an event called a “Slut Walk” in various cities around the world that are meant to give the message that it is not OK to sexually assault a woman because she wears immodest clothing. Usually, the women marching in these events make it a point to wear provocative clothing, but if a group of religious sisters were to march in such an event, they wouldn’t be marching in favor of immodest dress, provided they were modestly clothed themselves. They’d be marching against using immodest dress as an excuse to rape someone. In fact, their obvious rejection of immodest dress could serve as a very stark statement of the truth that modest dress is meant to honor the body of a person who has inherent dignity and against the falsehood that human dignity is earned by dressing a certain way or can be lost because someone fails to dress in a certain way.
Likewise, a parade having to do with gays might not be a march in favor of acting out on same-sex attraction. It could only be about opposing unjust discrimination because of real or perceived sexual orientation. Since the Church teaches that “every sign of unjust discrimination in their regard to be avoided” with respect to persons with homosexual tendencies, it would be moral for a Catholic to march in favor of just protections in employment, housing and so on for homosexual persons, since of course they all need a place to live and a way to make a living as much as anyone else.
I hope that helps.
Your in a tough spot then I think.
