I think a more relevant question would be something like: Does watching rape porn make people more likely to rape? Does watching porn make people more or less likely to rape? Or something similar to that.
I'm sure there are places where porn has been illegal but later become legal, looking at how it changed the rape statistics might give some weak evidence (though correlation is not the same as causation of course).
Advertising doesn't just show the product being consumed (not that modern pornography shows just sex). But, take cola commercials as an example. You barely see the product in these advertisements anymore, just the branding associated with the product. What you see are actionable items to associate with the item; sexy men and women, a luxurious lifestyle, fun, friends, wealth. They're associating a lifestyle with the brand in a Pavlovian way, so when you see the logo on the side of the box, or the can, you don't even think cola anymore, you think lifestyle. That's what a hundred years of advertising has taught us.
The closer comparison one can make the better, right?
Drinking coca cola isn't illegal or even looked down upon. Rape porn isn't advertisement for rape and is not meant to encourage people to rape. Coca cola advertisement/product placements is designed to make people buy it more.
The two cases are in my opinion very different.
Do you suggest rape porn or rape scenes in movies promote more rape in the real world? What about violence in video games? I don't claim to know the answer, but I've thought that was disproved (though I haven't really looked into it).
I'm sure there are places where porn has been illegal but later become legal, looking at how it changed the rape statistics might give some weak evidence (though correlation is not the same as causation of course).