Sure that's true, but that's different than rape. The unwanted(?) attention the woman is going to get means getting hit on, stared at, cat called, possibly even an unwanted physical contact, like a squeeze. Now while you could categorize the unwanted physical contact as sexual assault (it legally is), it's not on the same order as rape.
The myth is that rapists are just super horny guys who can't control themselves. They are far more motivated by insecurities and a desire to physically dominate a woman, violently if necessary, to achieve a feeling of power and superiority. Rape is also such an extreme crime that rapists don't often get the chance to be picky about what their victim is wearing, or often even who she is--it's hard enough for them to isolate a woman in a situation where she can be raped without the rapist being caught that there aren't too many opportunities to pick and choose what she's wearing--even if she's known to the attacker, which she usually is.
Certainly a woman who dresses slutty is going to get some extra attention--but the notion that it will amount to rape is just wrong.