When the First Amendment was authored, I suspect people thought public property was going to be where the largest audience was, with the town hall and park and square and what not being the main platform for discussion. Reaching the crowd meant going out with a handbell or standing on a box passing out pamphlets. Stopping the government from arresting someone advertising in the town square was more important than stopping a shop from kicking out a customer they didn't like.

But that's not the case now. The platforms hosting your work are privately owned, the large community websites/social networks/whatever with millions or billions of users are privately owned, and a larger portion of real life locations people frequent are privately owned too.

The way society is going seems to be making the amendment less and less relevant as time goes on.