I'd like to think that the vast majority of those who immediately turn to 'Well, the girl shouldn't look so attractive' do so more out of a desire to feel like there is some level of control over the situation, or more accurately over their own safety. Society likes to have things quantified, explained, given closure on the what, when, where, and especially the 'Why.' The thing is, it's all but impossible to predict the variables of an inherently unknown number of people you haven't met before who may or may not harbor ill will towards you; the next person you have a one night stand with, regardless of gender, might leave you waking up naked with all your shit stolen. Hell, the next person you let into your HOUSE might slide a knife between your ribs because of some undefined murderous intent or mental illness. The next guy you sit beside on the public bus might slit your throat. Statistically highly unlikely, of course, but still POSSIBLE, and in many cases this violence can come from someone you don't know, who doesn't know you, and is only doing this to you because you're a target of convenience. This makes it inherently difficult to predict or 'prevent' a perpetrator from... well, perpetrating, because you probably won't know his intent or motives until the deed is already done. =P
So attention is focused on the only relatively 'known' variable, the woman who has been, or might be, the victim of such an assault, whether it was her outfit, where she was at the time, or the state she was in. The reason for all this is because it brings an odd sense of comfort to just think 'Oh, well, she had too much alcohol, of COURSE she got sexually assaulted,' or 'Oh, she was dressed provocatively, of course men want to have sex with her,' etc, etc. Because by saying this, there's the flip side, the 'If I (or those I care about) DON'T do these things, then obviously they'll be totally safe, because they weren't putting themselves in such a situation.' By that same token, when you read about people who tried to sell something on Craigslist or the like, agreed to meet someone in a vacant lot to make the exchange, and ended up getting shot and/or killed with the object itself stolen, there's always the 'Well, yeah, they went to meet a complete stranger in the middle of the night in a deserted place, of COURSE that happened!' Because the mirror to that is 'I'd never meet a complete stranger in the middle of the night in a deserted place, I'm perfectly safe.'
And to be fair, there are always things you can do to reduce the chance of something bad happening to you. Install bars and a security door in your home so people can't break in, avoid any shadowy places or alleyway entrances or really any deserted streets at all, never leave the house after the sun has gone down, don't dress in expensive looking clothes that might peg you as a good mugging target, never drink heavily in public venues regardless of gender or age, don't take the bait if someone tries to pick a fight with you, etc, etc. Doing some or all of these things will lessen the chance that you find yourself in a bad spot.
But bottom line is that the other half of the equation has to be dealt with, and that's that people who assault, steal, rape, and all manner of other things need to be reformed, detained, or otherwise handled. No matter how mild mannered someone is, no matter how 'properly' someone behaves, they will never be totally safe in society. Those who sexually assault a woman, no matter how drunk, stoned or otherwise out of her head she is, need to answer for it as the criminal they are, and the victim needs to be given full support and care, not a string of 'Well, You Should(n't) Haves'.
The question of educating potential victims on how they can best guard themselves is something I believe to be important, but note I say POTENTIAL victims. I.e. men and women who are settling into society and still finding their way. In a situation where we are dealing with a crime already committed then full attention, fury and condemnation should be dealt to the one who carried out the deed, not upon the one on whom the deed was carried out.
tl;dr: People crave feeling like they're in control of any situation, which is where I feel a lot of victim-blaming comes from, the idea of 'Well, if she didn't do x thing, she'd be safe.' (Replace 'she' with 'Me or my loved ones' in all these cases for the subtext.) But the truth is, society is inherently unsafe, and unpredictable, so while to a certain extent education is vital ('Don't Trust Strangers' or 'Put On A Seatbelt When Driving,') just as important if not more so is swift and decisive handling of the perpetrators of such crimes, be they rapists or dangerous/drunk drivers.
Zanten, Doer Of The Things
Unless He Forgets In Which Case Zanten, Forgetter Of The Things
Or He Procrascinates, In Which Case Zanten, Doer Of The Things Later
Or It Involves Moving Furniture, in Which Case Zanten, F*** You.