I guess it does seem like women are pretty harsh in general when it comes to male advances, and I think that's the reason for the initial fear that so many guys feel. It's that sense of 'she's going to chew me up and spit me out if I come onto her' - and everyone knows how fragile male egos are. A lot of men simply can't handle being told 'no' and they're afraid of being eaten alive as opposed to getting the gentle let down that most women really are cordial enough to give.
I tend to think it's because women get confronted with so many guys on a daily basis that they need to put up a wall. I can understand that though, since when I'm out and about I notice lots of leery men checking out attractive women and I think I'd be pretty weirded out if I were in their shoes. It's the same story when I've had a girlfriend and I see someone eyeing her up - it sparks a sense of annoyance and weariness within me. I do find that it's sort of half/half though, at least in my mind - for every woman I talk to who's distant and testy, the next will be decently warm and friendly.
What is important is to realize that if you do get the cold shoulder, it's nothing personal - nor could it ever be, as the woman brushing you off doesn't know you well enough for it to be. It's more a self-protection thing. Having said that, we live in a pretty shallow society, where having an obvious edge of some sort will make it easier for you to get your proverbial foot in the door. But that doesn't mean that regular guys have no chance. It just means you have to be creative and play your strong suits because it's true that everyone deserves happiness with someone they find attractive.
Ultimately I feel it's what I've said in the past - life is a numbers game, and the more you can network without fear, the better you'll do. Of course you'll be rejected along the way, but everyone gets rejected at some point, and you can never please everybody no matter how seemingly perfect you are. So remind yourself of your positive traits, work on some original openers, remember that a 'no' is no big deal, and get to practising.