Do you prohibit people from exercising their First Amendment rights on your own property?
I'll wager that you do, or certainly would if someone who you invited to be on your property decided to set up a 'soapbox' and harang those around him about the wonders of Liberalism as practiced by the late Soviet Union.
How can an inanimate concealed object that cannot be seen be compared to speech which can be heard? Your comparison is not plausible.