To say that anyone can be a photographer belittles the skill associated with a professional photographer. That’s akin to saying that you can hire anyone with a voice to be a singer. Sure, you can, but there’s a qualitative difference.
That aside, would there be any sign that the photographer could put on their door that would be illegal? No Blacks, No Jews, No Women, etc… If not, play that to the logical extreme; What if all photographers in town had the same sign? What services are appropriate to deny in entirety to a specific class of people.