Whatever it means, those words are not in the Constitution.
The Constitution recognizes the right the peaceably assemble, and the right of free speech.
Assembling, and assembling to speak, and assembling to speak to seek redress from the government, combine to infer a freedom of association.
Along with the right to peaceably assemble, comes the right to choose to NOT assemble. That's what is at issue here. People, on their own private property, are choosing to NOT assemble, and the people they choose to NOT assemble with do not like it.
-PJ
The bill of rights was a bad idea, and many thought so at the time, since the part about "The enumeration in the Constitution, of certain rights, shall not be construed to deny or disparage others retained by the people" often gets ignored.
/johnny