Dr. Ben Carson, a rising star in conservative circles, on Friday compared President Obama’s health-care law to slavery. “You know Obamacare is really I think the worst thing that has happened in this nation since slavery,” Carson, who is African American, said Friday in remarks at the Values Voter Summit in Washington. “And it is in a way, it is slavery in a way, because it is making all of us subservient to the government, and it was never about health care. It was about control.”