>1) These people are rare in the general population, and demand for their time is likely to be incredibly high. Therefore, they cannot be deployed everywhere, unlike machines.
A temporary problem solved by natural selection, technological augmentation, and increasing incentives. Perfect performers in any profession are hard to come by. Ambitious people still strive to get there.
>2) When confronted with a human being in a sales scenario, people have a chance to be on guard against potential manipulative behavior. When the sales scenario becomes ubiquitous and invisible, it is much harder for people to avoid being taken advantage of.
Because people don't understand technology or sales. In your reality, people should be on guard all the time because sales and marketing were already continuous, even before hidden cameras. In actual reality, most people don't care that much about being sold to as long as the sale itself it not abusive.
> 3) Ethics are not so absolute. Something that is only mildly bad at an individual level can have terrible results when thousands are doing it. (Littering, for instance, or illegal hunting/fishing.) This is known as a social trap, and it leads to negative outcomes for everyone involved.
Sure, but that omits the necessary step of justifying this behavior as being either mildly bad on an individual level or terrible on a mass scale, much less both. It is neither.
Also, I would add item 0: advances in technology mean that surveillance devices will only become smaller, cheaper, and more connected over time. The future you fear so much is, in fact, inevitable.