Read the opinion. The court accepted for the sake of argument that it was a mixed expression case - that is, that it involved some degree of expression by the baker - and then applied intermediate scrutiny to the matter, under which an infringement on a constitutional right by a facially neutral statute will be upheld if the statute directly advances a substantial interest of the state.
And yes, whether other people would recognize something as an expression of a particular person or not is a factor that is taken into account. Read the opinion.
This is not a defense. The question is not whether the opinion says this, the question is whether the opinion is reasonable, that is, internally consistent and consistent with principles of social and legal interaction on which consensus is clear; one cannot demonstrate that it's reasonable merely by citing or summarizing it any more than one can logically defend The Bible by citing The Bible. Also you have still not described your own objections to the law which you have described as "stupid", nor have you defended the idea that those who are paid to create expressions can be compelled to do so.
Merely stating that it's the law confuses indicative with subjunctive and is not a valid logical defense, else Dred Scott and Plessy v Ferguson, not to mention the Spanish Inquisition, the Divine Right of Kings, and the Levitical Code, would still be in effect.
Readers will reach their own conclusions.