Google doesn't want to slow it down. They just don't want to be associated with companies that are related to fraud. And, I think that this is a valid and correct choice for Google because they have their own brand to protect.
More specifically, Google doesn't want the SEC to hold them liable when they go after some of these fraudsters.
* sites abandoning adsense because they don't want to be associated with cryptocurrency
* users installing adblockers because they don't want to be running monero miners