Your internal view of the brand is being changed or challenged. This causes a type of psychological stress. The iPad is only a machine but Apple the brand has carefully created a brand with emotions feeling and thoughts around it.
People invest themselves in their ideas. the ad isn't concerning for what it does in the ad, but for how it is changing the internal feeling of the brand.
It is like remembering when thinking about a car changed for you. From just a car as a kid to something else, something with more meaning. It's why all car adverts are about emotions.
Firstly the brand feelings exist even with people who don't own anything to do with the brand. Again with the cars, car adverts mainly seek to install sentiment in non car owners.
Secondly, I think the ad "as art" on it's own is disturbing and menacing.
People invest themselves in their ideas. the ad isn't concerning for what it does in the ad, but for how it is changing the internal feeling of the brand.
It is like remembering when thinking about a car changed for you. From just a car as a kid to something else, something with more meaning. It's why all car adverts are about emotions.