Why is looking at thinly claded and/or sexually attractive women haram?

I never understood this. I am a Muslim and respect and enjoy looking at beautiful women (naturally). I don't understand why it is so bad to look at a woman. I feel a new modern Islam should promote women's freedom to dress the way they want, and for men to enjoy them. I don't see anything wrong if a man watches videos of sexually attractive women. *How could it possibly be haram?* She isn't naked, she isn't doing a sex tape or anything. Simply showing off her fit body in beautiful lingerie. Men watch it, enjoy it, and have fun with it. Some women also watch it and enjoy it. Can we not accept this as a new part of the modern Islam (women's freedom of clothing)? I don't see myself ever giving up enjoying women. I don't commit adultery, or drink, or smoke because I truly see a problem there. But freedom of dress for women and freedom for men to enjoy women, there is *zero* harm in that. I have nothing against women wearing bikinis (showing off how hard they worked on their bodies) rather than woman in burqa. And I don't have a problem with a woman dancing in front of men for their entertainment. What is wrong with that? Things have to make sense in a religion and this clearly does not. Any ideas?