This will not work while the cost of identifying and stopping bad ads is higher than that of creating new ads. The same reason robocalls and Nigerian email scam

This will not work while the cost of identifying and stopping bad ads is higher than that of creating new ads. The same reason robocalls and Nigerian email scams still exist. Google is in the best position to stop it, albeit with the spectre of a chilling effect. However even if Google completely cleaned house the bad ads would still exist because there are ad networks other than Google. I would suggesting holding website owners liable for the ads that appear on their sites. It makes it easier to identify who needs to be sued. The buck stops at the name in the URL bar.