The harm would be having to waste time on a court case of this type. What a bore.
I think it's the woke couple that brought the case all this way. Obviously, they don't want to employ the Christian guy to make their website any more. So I think they should just let it go.
I see no reason that everybody has to have the same moral priorities. If a Christian or a Moslem thinks his religion teaches him that he shouldn't advocate gay behaviour via the development of a website, so be it. In my view, it isn't the role of a society to force him to provide this service. Let different ideas exist. The opportunity emerges in the market for a gay website specialist to make a job for themselves.
If he had a monopoly on website development, I'd think differently. Or if it was a thing involving healthcare. But for a non-essential service where there are perfectly decent alternatives, I'd be with SCOTUS if they said refusing to provide a service of this type for this reason is entirely permissible.
Otherwise, you just have the law dictating everything. And I think a society is happier where the courts are not over-involved in stuff. The law works well when it is available for extreme nastiness or real harms, and it works badly when it dictates casual behaviour and it enforces conformity, even where not conforming is obnoxious.