Hmm. I think I need to clarify your position. 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.
This is a fine idea, but problematic in practice. To be a commons (public in the sense of unowned) a property must either be unused or freely used by all. The first is a waste, the second a potential disaster. Once use restrictions are imposed, the government (state, town, whatever) has claimed that property and is now its owner. The question now is whether the management of a resource is most efficient in the realm of politics or the realm of the private market. We all know the answer to that -- the market will deliver the better outcome.
It might be better to say that the assault on public morality by multiculturalism is facilitated by the attempt to treat public property as a commons when in reality it is state-owned property. To say that a governing body should manage a public space wisely is no different from saying that a private owner should do so. The question is which owner (the transitory members of a town council or a private landholder) has the proper incentives.
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.