That really is the business of the Advertising Standards Authority (ASA) rather than the media brand and platform hosting the ads.
If every website, newspaper, magazine or TV/radio station had to check every ad it wouldn't have any time or money over for actual content.
Media companies sign up for rules such as IASH, which stop inappropriate or offensive content or advertising.
The ASA investigates complaints on the actual advertising.
PC Advisor, does block many types of advertising independently - Wonga and the ilk, for example, which we find morally wrong.