premise: But you -- under your intermediate scrutiny test we would not be hypothesizing what might have been in Congress's mind. Your First Amendment test is a stringent one. You have to have an important purpose, and the means that you use is necessarily tied to that purpose. If you take that position, I don't see how you make the retroactive-prospective line work.
hypothesis: The retroactive-prospective line will not work.
reason:  The writer claims, "If you take that position, I don't see how you make the retroactive-prospective line work." But that doesn't mean it can't work or won't work. The model took the writer's opinion as fact.