If you aren't willing to buy a Mac anyway, how would the ads convince you to buy them? What the ads do is to try and get people who wouldn't ordinarily consider a Mac to at least consider them.
Usually, the point of an ad is to convince people to buy your product, especially people who don't already own one. If Mac want to increase their share of the market beyond it's current 2%, then it's going to have to convince some PC users to switch. The current ad campaign is more likely to elicit cheers and laughs from current Mac users (kinda like Algore cheerleading for the extremist left) than it is to convince a PC user to switch.