This isn't rocket science. What the CBO says is that 2 million people will leave the labor force because, now that Obamacare has broken the link between work and availability of insurance, they don't need to work anymore in order to continue being insured.
These people will no longer be in the labor force, and for the best of reasons: they've got enough money already.
The jobs they previously held will be taken by 2 million people who need jobs.
Or that already have jobs, and can grab a better job that's been vacated by the early retirees. But their jobs in turn will become vacant. Ultimately, you've got 2 million new jobs available for people who would otherwise be unemployed.
So this is reducing unemployment by 2 million people. 2 million people who had enough money to quit work, but kept on working because they needed insurance, get replaced by 2 million people who need the money.
That's a win all around. Four million people will live better lives as a result of this alone. And it'll be a boost to the economy, because the 2 million people who are willingly, eagerly leaving the labor force probably won't reduce their spending by much, and the 2 million people who go from unemployed to employed will damn sure spend more money, because they finally can. Their extra spending will create additional jobs, in addition to the 2 million jobs that are being reallocated in a beneficial way.
Conservatives are really having to look at this completely backwards to portray it as a bad thing. But that's how they make a living, I guess.