First, I did not say "freedom of speech is ...", but "you don't really have freedom of speech if ...". It's a bit like saying "you don't really have freedom of movement if you have a law abolishing the borders but at the same time another law that says that citizen will have their legs amputated". Of course, "freedom of movement" isn't "freedom of having your legs", but the point is that the GOAL of freedom of movement can be, in practice, impaired if you apply some rules that impair it.
The problem here is that "move along somewhere else" is impacted by this law: apparently (not 100% but some sentence in the text seems to say that), this law can say that every "somewhere else" can be forced to accept the mass of "shut up" people. So, there will be nowhere to go where they can speak freely, which, in practice, will force them to just not being able to exercise their freedom of speech right.
I really don't get people who are pro freedom of speech, but at the same time have no much problem will people being coerced, in one way or another, to not speak. Either they are hypocritical (and want to be able to impose their speech without caring about the speech of others), or they've released the substance for the shadows (they are putting values on an empty concept instead of focusing on the goal).