Haven't read that study yet. But even without giving the matter intensive study, I can easily conclude (at minimum) that porn is not a net positive for a community.
I would further argue that it is not neutral either. Sex and how it is portrayed cannot be neutral. Showing women or men naked in blatantly exaggerated (and sometimes degrading) positions of sexual arousal and gratification does not lift humanity, and is not artistic. It advances the view that permiscuous (did I spell that right?) sex is desirable, that the gift of sex is something to be displayed in the most base manner, and that women exist to fulfill that desire.
Add it up, and porn must be a net negative for a society that is invaded by it.