From here. I've always felt that the "true believers" of the Right Wing represent about 20% of the population, which was why Bush's approval ratings never dropped below 20%. So it is only reasonable to view the "angry" result as being that of these "true believers" who think that the passing of the Health Bill is the beginning of the People's Democratic Republic of America headed by Chairman Obama.
This is only an initial reaction, however. How people will view this bill will change as time goes by, and I'm not ruling out any movement towards the negative.