What is the most controversial provision of the patient protection and affordable care act which is sometimes referred to by it's the detractors as obamacare

The most controversial provision of the patient protection and Affordable Care Act which is sometimes referred to by its detractors as Obamacare is mandatory health insurance coverage. This is controversial because it would mean that those people who do not wish to buy insurance may be subject to a fine. 

The answer is ethnic groups.