I can see how you are amazed on how the issue is so divisive, ordinaryman if you see the world in a vacuum, outside any sort of social context. Of course porn (or some version) has been around for centuries, but women have been oppressed forever, too. So even though there may be many niche markets for certain types of porn, and some with consenting adults (as I am sure some is, rather like online dogging) porn has developed from the fundamental view of women being only valuable as sexual objects. I think anything that perpetuates this is damaging for everyone, male or female. Women grow up in the very same society as men, and so often we don't feel the injustice because it's all we've known.
One interesting study recently (must try to find it) showed that all humans are aroused by visual images of sex acts, even if they are not consciously aware of it, and that (hetersexual) women were in fact biologically/physiologically more aroused by more varied things than men: FM, FF, MM, monkeys, you name it. Unlike men who were only turned on by images that fit their own sexual preferences. This is so telling, I think. It shows that we've been socialised into thinking that porn is a man thing, as its main consumers are men - it's socially acceptable for men to watch it, go to lap dancing clubs etc. It clearly is not a biological drive for a man, it's a human thing to enjoy watching others have sex, it's just that women for centuries have been packaged as the main sexual comodities.