I am not a fan of these **** walks, looks like a large amount of attention seeking really.
Everyone is entitled to wear and behave how they want (within the law). Everybody should have enough common sense to know that doing certain things in certain places/situations may get you into trouble. You probably don't always deserve that trouble, but you have to be aware that there are a lot of idiots in the world who will do bad things for silly reasons.
Pick pocket warning signs are all around London, it's not telling you that by having nice items you are allowed to have them taken from your pocket, it's telling you to be wary and take care as there is a risk.
There are signs at some London train stations warning you about using your mobile phone openly due to the relatively high risk of mugging and robbery in that area. This isn't saying if you use a phone you deserve to be mugged, it's telling you to again be wary about where you are and what you're doing to minimise the risks you face.
The same things can apply to women. If you go around late at night getting drunk wearing slutty clothes that obviously garner a lot of attention for you (both good and bad no doubt), then you should realise that this is taking a risk. It doesn't mean you deserve to be raped, but it does mean that you're increasing the chances of the wrong kind of thing happening.
Unfortunately many of these people seem to think that being warned about the negative attention they may attract through dressing provocatively (it's surely called that for a reason) is sexism or telling them they deserve to be raped, which is completely untrue and wrong.