I don't think that those arguing against this bill's constitutionality have a leg to stand on.
I find the case
Gonzales v. Raich to be rather relevant to this question.
Full OpinionOf particular relevance here is Wickard v. Filburn,
317 U. S. 111, 127-128, where, in rejecting the appellee farmer's contention that Congress' admitted power to regulate the production of wheat for commerce did not authorize federal regulation of wheat production intended wholly for the appellee's own consumption, the Court established that Congress can regulate purely intrastate activity that is not itself "commercial," i.e., not produced for sale, if it concludes that failure to regulate that class of activity would undercut the regulation of the interstate market in that commodity. The similarities between this case and Wickard are striking. In both cases, the regulation is squarely within Congress' commerce power because production of the commodity meant for home consumption, be it wheat or marijuana, has a substantial effect on supply and demand in the national market for that commodity. In assessing the scope of Congress' Commerce Clause authority, the Court need not determine whether respondents' activities, taken in the aggregate, substantially affect interstate commerce in fact, but only whether a "rational basis" exists for so concluding.
I don't think that anyone can argue that Congress has a "rational basis" for concluding that people choosing not to purchase health insurance would have a substantial effect on insurance premiums, and therefore, interstate commerce.