Earlier quoted context omitted.
I don't expect you to back off of your take, but you should really consider how and why you came to this conclusion. If I put two different marketing messages on two different billboards to test whether one is more effective than the other, is that unethical non-consensual experimentation? If not, how is it different from A/B testing?
In strict terms yes, if you didn't get informed consent from your test subjects that would be unethical. Research has a lot of policies and systems set up to ensure that if your testing involves people, you must get informed consent from the persons before even trying to do the test, and it's really not hard to imagine why this is a stringent standard -- it's very easy to miss how "simple tests" can and often are adv…
If this is based on the possibility that one or more of the ads is harmful, how is it less ethical than the time-honored alternative, which is skipping the study and just running the ads?