I think this issue is why we have protected classes and why sexual orientation/preference/gender should be one.
When you say “graphic artists can reject any idea and they don’t have to justify it” the implication is that they can reject it for any reason which is not strictly true.
“I don’t feel like it” is a perfectly valid reason.
“I don’t like Black people” is not.
A photographer can choose not to do a job because they don’t feel like it, but not because it’s for a Black person or a Jewish person.
The issue here that is being overlooked in a lot of the discussion (but definitely is not being overlooked by the Supreme Court) is that LGBTQ people are not a protected class. Every time one of these cases pans out it sets another precedent that will be used to keep it that way.
It’s not the same as being forced to photograph a Trump rally or campaign photos. A far more apt comparison imo is race. Most people would agree that a business (any business) should not be able to exclude someone based on their race.