Actually, it's not stupid at all, if you're PETA. The Google Ad service lets advertisers specify some keywords to be associated with their banner, and the banner is then displayed on sites which are relevant to that keyword. PETA obviously specified that they wanted this banner targeted at a low-carb audience, so Google Ads is just doing its job -- it's not necessarily smart enough to know that the content of the banner is anti-low-carb. It's up to the site owner to report that an objectionable banner is being displayed.