I wonder if they would change their minds if the situation were reversed.

Imagine a christian goes into a trans-owned cake-shop and demands they make them a cake that says 'God hates tranny faggots". I bet they would see this as unreasonable, even though its the literal same situation, and say the trans person should not have to create a god hates trans cake.

What the law should be hear seem pretty obvious. It is discrimination to refuse to sell them any cake at all, such as a pre-made cake already in the fridge just because they are gay or trans (we established this definition during the end of segregation), but when you are demanding someone use their artistry to make you a custom cake, they should clearly be allowed to refuse to do so, as you are asking them to do something against their values, rather than just serve someone with different values