I can’t see forcing someone to work against their will.
I refused a call for air conditioning service from a known deadbeat. Am I discriminating? Are all deadbeats entitled to service on their air conditioners?
I refused to change a fan motor on a gas air conditioner. Simple job, but if I laid a wrench on it I was married to it and they were problematical.
Forcing someone to work against their will seems unconstitutional on the face of it.
I defend the right of the business to refuse service to people that violate my religious beliefs.
However, I would not refuse it generically.
If the couple stipulates that the vows are not performed in a Christian church and I nor any of family members must be present for the ceremony - only to set it up - I would consent to provide the service.
Most flowers are bisexual. They won’t care. I would also be careful to take photos/videos of the floral arrangement once I was done setting them up so that later I could not be accused of lining them up to spell FAG or some such. I would also leave a small, tasteful stack of business cards which would contain a Bible verse on them.