This will be an interesting episode. Dr. Althouse wonders if the unions know something about authority's willingness to enforce the law. Well, there are two things to know about it:
1) The policemen who might be making the arrests are part of a brother union.
2) The fine for simple assault is small enough that the union can readily pass the hat for it, if in fact the law is enforced.
What the unions know, in other words, is the product of more than a hundred years of leveraging violence as part of their politics. They're good at it, and this model once brought them astonishing gains. There's no reason it shouldn't be persuasive again, because people don't really like getting punched in the face.
During the period between the end of the Indian Wars and WWI, the US Army's main business was putting down labor strikes. After that corporations hired private armies to deal with them for a while. Finally, everyone surrendered. By now, the unions control the Democratic Party and the President of the United States is their firmest ally because he knows how important they are to him and his agenda.
I don't think the unions are the least bit afraid of the "grassroots," and why would they be? The grassroots aren't ready to stand up to violence, let alone to employ it themselves as part of a broader political agenda. They certainly aren't prepared to organize along those lines, as the unions have done and been doing for more than a century.
What are you 'grassroots' folks going to do about it? Tweet?