It's forcing a service by federal mandate, they're abusing the commerce clause by calling it a tax. Period, end of fucking story.
Well the Supreme Court has ruled the penalty a tax, which is within Constitutionally-granted Congressional power, so it is in fact Constitutional as decreed by the Supreme Court, the very body which the founders set up as the final say on the Constitutionality of legislation. A majority conservative Supreme Court no less. You are not mandated to buy health care; you are just made to pay a penalty if you don't.
“The greatness of a nation and its moral progress can be judged by the way its animals are treated.” - Mahatma Gandhi