So from my own point of view and opinion I agree this is one stupid ad campaign, BUT GM does have the right to print a ad campaign to generate money from perspective customers. It only takes one person to buy a automobile from reading a advertisement to make said advertisement a success.
The problem I have in the controversial ad is using a group of people like bike riders and showing them as losers or geeks to pump up there product. The reason its a bad idea is because this stereotype no longer fits anymore. Many types of people ride bicycles for many different reasons. I believe the car companies are seeing a drastic drop in sales to individuals around college campuses because they have to fight against the bicycle and people walking and this makes them mad. So they feel they must show these individuals in a light to lower them to a class of people that might not actually fit the real person.
So does GM have the right to make stereotype style advertisements? Yes they do. The only stupid thing is, is that there perception is drastically warped and out of date. I believe this ad campaign stunt seriously blew up in their own face, because they are stuck in an era where this style of stereotyping would possibly be relevant, which it no longer is.