I believe that the key of the message was that the advertisement companies gather a plenty of personal data and vulnerable groups are very easy to find and target. The same private data is also useful for "all the people who host scam sites on the cloud".
This. The more ad platform becomes accurate, the more ads will exploit vulnerabilities in human mind. Some might believe they don't have such vulnerabilities, but there can be some in subconscious level. Ad tech is basically PSYOP and people really should be on guard.
The author of the post specifically (you read the article, didn't you?) said:
> The thing is, I think advertising is positive, and I think my individual contribution is positive. I'm open to being convinced on this: if I'm causing harm through my work I would like to know about it.
Then goes on to not mention a single example of harm being caused through their work, like virtually all articles that attempt to defend the advertising industry's practices. I thought I'd list a few.
You make cars? You focus on good things like driving to a vacation, but what about all the cars used in drive by shootings?
You sell cloud services? You talk about the great websites, but what about all the people who host scam sites on the cloud?
You write monitoring software? What about all the people who monitor ad services?