I just don't understand this, personally. And here is reason #1 and reason #2 why:
Are they trying to make a political statement or get a cake?
If I'm forced to make a cake for someone I don't agree with, I'll do it and without the urine/semen/salt/whatever……but I won't bother trying to do a good job on it. I'd explain that I really don't want to do it, but if you insist, these are the terms. Likewise, if I'm a photographer, I'm just going to spray and pray half-assed and not bother cleaning anything up on photoshop later.
I just don't understand why, in any service industry, you'd force someone who doesn't want your business to serve you. I want someone who truly wants to do what I'm looking for.