Hey, long time no see.
Hey man. How's tricks in tulipville? I've been trying to finish my friggin book, sell a house, etc. etc.
There is nothing which can be exhibited, no matter how odious to anyone, which can actually hurt the exhibitor.
This statement is clearly not true as performers in all sorts of exhibitions hurt themselves. Athletes injure themselves. Stuntmen die performing dangerous stunts.
Assuming we restrict your statement to sex acts, sex performers can injure themselves physcially, and can contract include STDs or other diseases (hep B & C) which can harm them or even kill them(your namesake John Holmes for example).
In exhibiting or viewing snuff, how is the exhibitor or the viewer harmed?
The exhibitor is killed. In BDSM the exibitor is physically beaten or tortured in a manner that causes pain, leaves bruises, burns, etc. I think that constitutes physical harm.
AbE: I might add that snuff isn't sexual expression, it's violence.
You say tomato. Surely we can both agree that one person's 'violence' is another persons sex fantasy? If we do, I don't see how you can just dismiss snuff films as not harming the exhibitor.