Rhetoric? Reed (the show organizer) changed the rules at the last minute to forbid the sale or display of so-called 'assault weapons', which adversely affected many of the firearms dealers and manufacturers who'd booked space at their show.
If they won't be allowed to display and sell their best selling goods, what is the point of following through by attending? They're going to be financially injured by Reed's last minute decision. I'll bet dollars to donuts that some of these companies already have letters from their attorneys en route to Reed's offices.
The paid for a table not a propaganda position.
A POTUS does not necessarily possess that unless people grant it. This POTUS exercises it even when permission is not granted. The boycotting vendors granted the usurper power when they refused to show up and do their normal thing, in spite of the usurper.