Laziness comes to mind. Do a porn user have anything else better to do? If the answer is no, well, that does say something about that person. Porn does not make you a better person. It is a waste of time.
Yet -- it is very addictive. The opium den of our time.
Multiply that "laziness" times a few tens of millions, and we have a social problem.
Sloth does kill societies. Societies where basic human things such as, in stat case the sexual drive, get fulfilled too easy, on the cheap, are societies that regress.
Porn is individually a waste, individually harmful for many reasons, and socially a danger -- a harm.
So if it hurts the individual, let them pay the price. Mind your own business.