The idea that it's wrong to use slavery as a cheap labor force is also modern and outside historical norms. Just because it's historically prevalent doesn't make something right or even good/acceptable. Some things based on historical norms are good. Some clearly aren't. And it seems to me a bit disingenuous to ignore the technological changes and the speed, pervasiveness, and invasiveness with which advertising is now done compared to the historical context being appealed to. Even if one grants that advertising wasn't "as bad" back then, that doesn't make what we have now acceptable.