You are assuming that justices take a law and the constitution and make decisions in a vacuum. They don't. They also consider prior legal precedents and Roberts said many times in his confirmation hearings that he would do that. Scalia and Thomas do much less of that and have more inspiring rulings that throw out those FDR precedents.
The legal precedents (since FDR ) that are consistent with this are :
1) targeted tax credits, 2) Medicare
Judges have grown the Constitution (Federal power) greatly since FDR.
Using the power to income tax to reward and punish us has been used for decades, this personal mandate is new only in that it is a reverse tax credit(it has no penalty for not paying it) , and a weak one too,
I can walk through an example, I had some insulation added to my house and got a tax deduction for doing that. So I paid less taxes for buying something that the government wanted-me to do. Do I like this?? NO! But it's the country we live in.
You were not forced to add insulation to your home.