IMHO, I think you miss the bigger point. In a controlling society like Roman society was - a police state, albeit "fun" police state (bread and circuses?) - it didn't matter what the views of the "common man" were. Those who were in control were hedons - lovers of themselves and pleasures - this lead by and large to the decline of the Empire as a whole.
Rome was not really a "police state." Certainly, it wasn't a representative democracy. However, the government did not really intrude into the daily lives of citizens to a great degree, probably less than in America today. Furthermore, the views of the common man were important to the authorities, especally in Rome itself, where fear of the Mob tempered the decisions of the Emperor himself.
Those who were in control were hedons - lovers of themselves and pleasures - this lead by and large to the decline of the Empire as a whole.
Again, this view of the ruling classes in Rome is based on the decadent excess of a very few. Scandalous behavior by a few at the top of a society is not an accurate gauge of the morals of a society. If you only judged the morality of American society by looking at rich NY socialites, corrupt DC politicians and libertine Hollywood celebrities, you'd conclude that America was rapidly sliding into moral collapse, too.
And, if anything, the two main causes of Roman decline were Christianity and lead pipes.