The point here concerns the nature of toleration. A tolerant society is not one in which everyone shares an easygoing permissive morality that sees nothing wrong with any kind of sexual conduct and which gets het up only about animals. A tolerant society is one in which people swallow their indignation for the sake of public peace. It is one in which the public space is protected by an overarching principle which does not forbid disapproval, but rather commands us to contain it. There is toleration only where that which is disapproved is also allowed.
This raises the question of what we mean by distinguishing the public and the private spheres. Some actions, we believe, are permissible in private but not in public. Undressing is one of them. And the concept of decency is absolutely
essential to defining the distinction between the permissible and the impermissible. There is nothing indecent about the act of undressing in private - not, at least, in the normal circumstances in which this act occurs. There is nothing indecent about the love-making of husband and wife in private. But when these acts are put on display they take on another character. They lose their innocence; they become an affront, a challenge and an invitation to states of mind that have no place in the public sphere, and no place in the private sphere either - voyeuristic states which most people regard as repugnant, without necessarily overcoming thereby the temptation to indulge in them.
Now it is here that we begin to see the significance of the word "public" in the phrase "public morality". The public sphere has its own moral norms. There are things which, while innocent enough in private, lose their innocence when put on display. They lose their innocence because they invade the emotions and the peace of mind of those who observe them, upsetting the delicate balance on which the routines of society depend. Obscenity is the paradigm case of this - though one that it is increasingly difficult to see for what it is, namely, as an invasion not only of the public sphere, but also of the privacy of those who inhabit it. The obscene performance is one that puts something private on public display. It breaks through the barrier between public and private, violating the sense of decorum without which people cannot maintain the objectivity and distance from each other on which the public sphere depends.