Why is art of Europeans being called pornography but art of Africans not?

What I do find strange is when white people post images of naked black people in africa, there isn't a reaction that its porn, its "just the way they are" you can find total naked or topless women in major publications. But when I show images of naked or half naked white women its not "just the way they are" but automatically porn. 

Its almost like a subtle maybe unconscious way of elevating white women over african or black women as somehow being more deserving of being shown with clothes or covered up because their nakedness or sexuality is more valuable or something. I don't know, something about all these comments about porn rub me the wrong way.