I’m not going to spend time to design websites for churches and other religious groups even for compensation. Artistic or engineering services are not beholden to anti discrimination doctrine the same way that hiring, retail, and public services are because the job requires you to make things to order, and if I fundamentally disagree with the order then I can just refuse the job.
It goes both ways. If these people can refuse doing paid design work for gay weddings, I can refuse doing paid design work for Christian weddings or arranged marriages. If I was forced to do so I’d sooner quit. That’s the point I think you’re not getting. If someone has the right to quit doing the work they do for any reason, they also have a right to refuse to work for anyone, and that fundamentally includes contracting work, not just direct employment.
TL;DR: if I can refuse a job offer for any reason, or quit my job for any reason, then I can refuse to do a freelance contract for any reason.
I think the term “birth certificate” needs to be renamed