The experts say it's bad.
They don't all say that. There are certainly some who do but there are just as many who say there is no harm and it's all just their own personal moralism and the ones who say it don't have much to back up the idea that it's bad and can't even answer what concretely would happen. And yes, there are studies that show negative associations with pornography and expectations but there is no evidence isn't worse than any other fiction. — That's in general the issue with these “harm” studies. One can show “harm” of pretty much any activity whatsoever by just cherry picking the harmful parts. The object is to show that it is more harmful than many things already allowed and common.
There are very few places where this is the case and it's illegal for children to watch pornography. For one: they very often aren't even considered criminally culpable before their teens so nothing is illegal for them. Where do you live that you believe this is illegal because I'm going to say it probably isn't and you misunderstood something.
I think it's probably better for them to not have their developing brains saturated with porn designed to stimulate jaded 30-something sex addicts. For example, step-sibling, choking, anilingus, calling each other "mommy" and "daddy"...that kind of stuff...
Perhap, but you can say the same thing about every piece of fiction ever and certainly religion. Religion is always the big reason why I don't trust any “think of the children” rhetoric. No one who sits idly by as children are allowed not only into religion, but allowed to be forced into religion can claim to “care about the children”. If you want to protect children, the first step is to make it illegal for anyone to attend any religious meeting before say the age of 12. If you believe people under 12 can't view pornography because it messes with them, they should certainly not be allowed to participate in religion, and especially not be forced to against their will which is quite common.
While I may fully grasp the intent of that specific law, I think it's a reasonable restriction. Also, life is just easier when you demand your kids follow the law..."Sorry buddy, I'm not the one saying you can't look at those titties....it's the federal government! Blame Donald Trump...he could let you see them, but he doesn't want you to!"
Again, really the only places where it's illegal for children to view pornography are the places where it's generally illegal to view it altogether and children are not generally considered criminally culpable to begin with.