Of course not everybody is systematically hurt nor did I claim that. About 11% of porn users are addicts. Porn addiction is real and incredibly difficult. But even when you are not addicted, regular porn usage has negative effects on mental health (lower impulse control, higher rates of depression and anxiety). It stands to reason that this effect would be exaggerated in children and teenagers.

At best, pornography is akin to alcohol and cigarettes. We regulate the ability of minors to access these things for obvious reasons. I see no reason why internet pornography is different.