Unpopular opinion: Ads by themselves are unethical. Whether targeted, contextual, or just randomly applied. Ads are psychological warfare against a populace using their very nature against them. All in an effort to get them to change their behavior in a way that's going to be detrimental to them. Either they stop looking for alternatives, or they make purchases they don't need to (see: toothpaste consumption rates).…
Is a doctor telling you to brush 2x a day an ad for toothpaste? What about their suggestion that you floss more? Those are aligned with your well being, but will increase your consumption.
> change their behavior in a way that's going to be detrimental to them.
This seems obviously wrong. The implication here is that anything advertised must be bad for the target. From an econ perspective this means that you reject the idea of comparative advantage.