When it's innocuous, such as Google thinking I'm interested in _women's_ fashion and showing me ads for women's clothing sites since I've indicated an interest in fashionable clothing, it's not a bad thing(this is actually what happens!). But imagine if Google's profile of me indicated an interest in something dark like fascism or racism, and they sold that data on which later resulted in me losing job opportunities or credit. That would be a really bad thing, because their highly inaccurate algorithm had a negative impact on my life.

The slippery slope is slippery because there are a lot of downward steps, not because there's one big step. Companies already buy your credit score and financials before deciding whether to hire you. Imagine if they bought your entire Google profile and used that too? It's about as accurate as a personality test and there's no way to dispute it.

It's worse than Social Credit Scores because Google doesn't even admit they have these profiles of you, yet they sell the data as accurate.