"I don't believe there is anything at all wrong with wanting to look at ethically produced beautiful/sexy pictures of girls. In fact, the opposite really. If, OTOH, someone wants to look at and get off on photographs of abuse and harm, whilst their action in doing so is not itelf causing the harm unless linked to demand, it is revealing something very wrong and sick within them."

This sounds a lot like the pot calling the kettle blacker enough instead of defending being black as a basic right. There is very little difference between your statement and "If someone wants to look at and get off on photographs of children, (because it's something I don't want) it is revealing something very wrong and sick within them." Adult-on-adult rape fantasies (both as women fantasizing being raped and men fantasizing doing the raping) were recognized as common, normal, and harmless long ago, at least in a society that demonizes sex to begin with, and I see no reason to think it would be any different just by changing the ages except perhaps even more common due to the extra demonization of all sex with children. I'd rather draw the line so I'm defending everyone who doesn't actually hurt anyone, instead of trying to draw the line just past everything I want to do, while calling everyone who is any more different than that 'sick'.