What a sanctimonious statement.
You've missed the important question: Is it a true statement? And the answer is yes, because, at the very least, cohabitation represents a public scandal.
Can you provide a scenario where cohabitation would not be wrong? I can think of one or two where, for example, your small plane crashes in Alaska near an abandoned house. To survive the cold, you must sleep together with another survivor of the crash, a member of the opposite sex, in the cabin overnight.
But that isn't the usual case.
I can easily see this argument being put forward as a reason why cohabitation is right in all cases. After all, it makes just as much sense as the argument that 1.3 MILLION children a year should be butchered because a few thousand rape victims become pregnant.
If the public decided not to be scandalized, is it still wrong?