The Conservatives on the Court absolutely agree that Roberts' rewrote the law. They give their reasoning. It's devastating to Roberts' illogical opinion, and to his defenders.
If you still won't read the whole opinion, here is a summary of the dissent's disection of the tax argument: http://washingtonexaminer.com/dissent-scolds-scotus-for-vast-judicial-overreaching/article/2500927