If you believe that prostitution is immoral because it involves society forcing a person to be sexually penetrated to make a living
But that's not why most people think prostitution is immoral? There is an observable coercion by one leader to a prostitute; the word "pimp" gets used a lot.
What if you're viewing pornography made by a company that does not pay a living wage to its actors? Is that any different from a PETA supporter wearing a fur coat?
If TNF is talking about breaching a right, your example is talking about hypocrisy, or insincerity. And maybe your whole argument is based on insincerity of the pornography viewer, but that is a narrow moral position you're taking. It is not compatible with the utilitarian arguments made by Tweed, Lief and others.
Furthermore, arguing on insincerity would make it harder to claim pornography as a total moral wrong. Maybe a viewer pays good money to ensure his porn is made with professional actors in a controlled environment. That seems to solve the problem you posed.
I have a very hard time seeing how pornography can be a categorical wrong ... the secular view is that pornography has to infringe on a right, so probably the right of a person to her body. Anyone with references to arguments from scripture would aid this discussion.