Nothing I write here should be taken as in any way condoning lust. Lust (by which I mean something along the lines of "dwelling on the idea of having sexual intimacy with someone you're not married to") is wrong, but I don't expect non-Christians to agree with me on that at all, and discussing why lust is wrong is probably the subject for another time.
There's a common line among some people (and I used to be one of them) that men lusting is partly the fault of women for showing so much flesh. Sheikh Taj el-Din al-Hilali went much much much too far down that road, and Scott Adams lampooned him brilliantly for it. Yeah, I know it's a bit old news. I've been wanting to write this for over a month.
Al-Hilali was obviously wrong. Women wearing revealing clothing might not be the most loving thing to do if there are men around who have problems with lust (and most men do), but it doesn't force them to lust and it doesn't make them rape you. That's their fault. But if he was wrong, if it's actually mens choice whether they lust or not, if women wearing revealing clothing isn't intrinsically wrong, why is pornography wrong?
Here's another angle, which sheds some useful light on the situation. Paul wrote:
everything God created is good, and nothing is to be rejected if it is received with thanksgiving
1 Timothy 4:4, NIV
God created naked women (Genesis 2:22,25). So if everything God created is good, surely that means that the naked female form is good and is not to be rejected. So why is pornography wrong?
The answer, and one solution to lust, is in the verse. Everything God created is good, and nothing is to be rejected if it is received with thanksgiving.
I used to struggle a lot with lust. I still do, but a lot less than I used to. One of the ways I used to try and deal with lust was avoiding pictures of women wearing revealing clothes or no clothes at all. That's a fairly common approach among Christian men. There were loads of problems with that. I've got a very good memory and (at times) an overactive imagination. I can avoid actual images in my own space, but I can't avoid them in public space, and I can't avoid women wearing revealing clothes without cutting myself off from the world. So just trying to cut off the supply of images actually had very little effect.
So what about thanking God for them? After all, God made naked women. I find that if I see an attractive woman wearing suggestive clothing, and I thank God for making attractive women, it gets my whole attitude much more right, and I am much less likely to want to treat the women in ways that the God who made them would disapprove of. It also makes my attitude to women much healthier.
Here's another slant on it. In Romans 1, Paul has all kinds of sin stemming from just two - ingratitude and failing to worship God.
The wrath of God is being revealed from heaven against all the godlessness and wickedness of men who suppress the truth by their wickedness, since what may be known about God is plain to them, because God has made it plain to them. For since the creation of the world God's invisible qualities—his eternal power and divine nature—have been clearly seen, being understood from what has been made, so that men are without excuse.
For although they knew God, they neither glorified him as God nor gave thanks to him, but their thinking became futile and their foolish hearts were darkened....
Romans 1:18-21, NIV
Paul then goes on to list loads of consequences and ways that the sin works itself out in people's lives. But if the essence of sin is ingratitude and failing to thank God, then isn't the essence of lust failing to thank God for attractive people and so want to experience them in the way that God designed? So how better to combat that than by thanking God for people instead of lusting after them?
So, my view is that pornography isn't wrong in itself. But if someone wants to look at pornography (of the sex they're attracted to), there's at least a 99% probability that their motivations are lustful and therefore wrong.
Oh yes, and a quick random plug for XXXChurch.com - #1 Christian Porn Site, if only because of the name.