On the contrary, my knowledge of history is sufficiently superficial that it fails to show him wrong. Perhaps you could provide some evidence?
What evidence is there that people are dressing more conservatively and that rape hasn't reduced?
The point wasn't that people are dressing more conservatively over time, but that if you go through time backwards, from the present towards the 1800's, holy crap, you start seeing more and more clothes on women the farther back in time you go. But you don't see rape disappearing or anything.
In fact, pretty much the only going down effect you see as you go back in time or across geography to some of the more benighted places, has to do more with stuff like
- whether certain kinds of assaults were even recognized as rape at all (e.g., yeah, before marital rape was even recognized as rape, the rape numbers were a lot lower)
- how easy it was to get out of a rape accusation (at least as late as 1966 when a study on the topic was written, even having a drink with the accused could be considered pretty much consent or having a bad enough character to not warrant convicting the rapist; and sadly we're still not completely in the clear for that kind of thinking)
- how much of a stigma it means for the victim to report it (which is why the reported rape incidence in Saudi Arabia for example is virtually nonexistent; but even in the west it's the most under-reported crime.)
In effect, most of the blaming the victim mentality seems to me to not actually do much to prevent anything. People were raped even when they were wearing victorian era dresses, and people are raped even when they wear burqas. What it actually does is just keep them from reporting it, and/or allow more rapists to go free.
The more we go back in time, the more we find juries deciding that although the victim did get screwed without consent, it's her own damned fault for whatever passed at the time as a sign of having low morals. You don't see what you'd expect, namely people going, "hey, she was covered from neck to ankles, so for Christ's sake, there's no way to pin that on her", but it just proportionally lowers the bar for what qualifies as being practically begging for it. You see more and more cases where the victim was ruled to be practically begging for it because she had a drink at a bar, or was smoking (until a tobacco industry campaign changed that, yes, a woman smoking was a sign of being some kind of slut), or had a reputation of having had extramarital sex (so then I guess then rape was free game too), or whatever.
In effect, that kind of placing expectations on the victim is counter-productive. Historically, the higher such expectations to avoid rape by not giving all the slutty signs were, the higher the expectation also was that if you got raped you must have given some signs that you're available. It even follows logically. If X=>Y then !Y=>!X. If one actually expects that there is some kind of dressing or behaviour that prevents rape, then if it didn't prevent rape, well, obviously she wasn't doing the right thing. Even if one has to promote seeing her ankles to a sign of her being available.
And it's not just for rape. The higher the expectations of a woman's "proper" behaviour were, just the more mundane were the things that were supposed to signal she's a nymphomaniac looking to get laid. I mean, when I mentioned eating chocolate or reading novels as being considered symptoms of it, I mean literally clinically, those were once considered symptoms of nymphomania. See, for example, Bienville in his 1771 treatise that coined the name of the "disease."
Which ties again to rape and rape reporting: throughout the 1800's you could actually be commited to a mental institution for being suspected of nymphomania, and one of the things that could get one committed was... reporting a rape. That's what one gets when people expect that whoever got raped must have somehow invited it. (Treatments included cold baths, enemas, induced vomiting, leeches applied... err... you know... down there, and could go all the way to genital mutilation.) Not that it stopped there, as the accusation of nymphomania was trotted out extensively in rape trials throughout the 60's and 70's.
What I'm saying is that really, looking back at it, I don't see provocative attires or showing breasts and legs as making much of a difference. You don't see rape taking a drop in the mid-70's when miniskirts went out of fashion, for example. The difference in rape incidents per capita has more to do with the relaxation of that kind of kicking the victim while she's down, than with anything fashion-related. Dress coverage going up and down just resulted in a proportional shift in what counts as inviting sex anyway.
