Also, as vague as "community standards" are, it does seem to me that they have some value in regulation. For instance, would you be in favor of allowing pornographic billboards in your town? What if the porn was political in nature?

I would still say that in that case, freedom of expression must be balanced against the community's moral standards. That may be vague, but it's real; I think there would be a pretty broad consensus among parents of all religious stripes, for example, that they don't want such billboards up where their children would see them.