She's beautiful. What's so wrong about appreciating someone's body? You don't see this kind of reaction to nude male models - that is where the real sexism is, IMO.
Why is the fact that it's from a nude shot considered demeaning? Because it's from a porno magazine? So what? I could kind of understand if it was a segment of an image from a hardcore scene but the full photo is actually quite tasteful.
If I ever get the opportunity, I'll use a crop from a nude male photo to prove my point. I would bet a year's salary that there would be no backlash.
There are far bigger issues in the world to be indignant about than this. We have people dying of thirst and hunger when we technically have enough resources to feed every person on the planet yet there are individuals full of anger regarding trivialities like this where everything is consensual, nobody was hurt and nothing bad happened.
I believe that the correct term for this is "theatre of the absurd".
By this logic, one could never discuss anything other than poverty, famine, and other terrible plights upon humanity.
Yet here we are, talking about such a variety of different topics.