Do my liberal friends support Congress really having this much power? Would they like a future conservative Congress to mandate every American buy a gun under similar constitutional logic?
The Patient Protection and Affordable Care Act (aka ObamaCare) includes what it calls an "individual responsibility requirement" that all persons buy health insurance from a private company. Congress justified this mandate under its power to regulate commerce among the several states…
In this way, the statute speciously tries to convert inactivity into the "activity" of making a "decision." By this reasoning, your "decision" not to take a job, not to sell your house, or not to buy a Chevrolet is an "activity that is commercial and economic in nature" that can be mandated by Congress.
It is true that the Supreme Court has interpreted the Commerce Clause broadly enough to reach wholly intrastate economic "activity" that substantially affects interstate commerce. But the Court has never upheld a requirement that individuals who are doing nothing must engage in economic activity by entering into a contractual relationship with a private company. Such a claim of power is literally unprecedented.