Here is my very simplistic take. You will have to pardon me for referencing the actual text of the Constitution -- I know this is passe in our modern era (jeez, I am probably a tenther too). The issue looks pretty straight-forward to me, for two reasons
- Congress shall make no law ... abridging the freedom of speech. Doesn't say by whom or for what. There are no modifiers. Doesn't say "except when individuals organize themselves into a corporation."
- Congress shall make no law ... abridging ...the right of the people peaceably to assemble. So Congress can make no law restricting free speech and it can make no law restricting assembly but somehow it can make laws restricting free speech of people who have assembled?