The Constitution protects you from THE GOVT infringing upon your free speech "Congress shall make no law....". It has nothing to do with any company or anyone else limiting your speech. That's really a middle school level concept but since our education system removed basic civics courses a few decades ago we 'Mericuns are amazingly ignorant. That's they we they like it I think, so they can claim this or that is in the Constitution (despite it not being there) and ignoring what is present.
Their actions had nothing to do with the fake email (or real email) from Bradgator, that was simply an excuse. We knew they weren't going to fix the forums, email complaints or not.
That site always sucked. Their software was worthless a decade ago.