[annalex]

If I'm understanding you correctly, you're saying that a purely private property society may be desirable but that until then, we still need to define the proper use of our remaining public space.

No, in the quoted by you statement I am saying that regardless of whether we have a purely private property society we need to define the proper use of the space that welcomes unsolicited cultural messages; and that such space will become available from either a government or a private party.

[Entelechy]

we need to define the proper use of the space that welcomes unsolicited cultural messages;

This only becomes an issue of individual rights if we assume that public spaces must be treated as a commons (something I think we both reject). In any other circumstance, there is a landowner (either the govt. or a private individual) and that person or people has control over use of the public space.

Now it may be more civil to conform to the greater community when managing a public space -- but it is not a rights violation to do otherwise.