I'd be more worried about a child turning on FOX News during the day time and becoming desensitized to gun crime, hate crimes, racial prejudice, casual violence, rape, terrorism, homophobia, transphobia, sexism, political scaremongering, corporate greed, and media manipulation. I don't think the answer is to hide news behind a paywall though.
Here is the thing we actually have more than 30 years of research in scores of studies that show there isn't a relationship between exposure to violence in the media (TV, movie, video games) and kids behavior. At macro level despite an explosion of violence in the media and coverage of the all the things you list, the trends are the right direction. Violence is roughly 1/2 in the US of what it was 25 years ago, and sharply down in most places in the west. Homophobia, hate crimes, racial prejudice, gun crimes etc are all way down. In the US, the biggest decrease in violence is among young men 15-19. My theory (no proof) is that a generation ago bored teenager boys were out doing Grand Theft auto (It was a hell of a lot easier to hotwire car back then than it is today), today kids are inside playing GTA on their Xbox. So while your worry is understandable, the social science says your intuition is wrong.
I agree that young children do deserve to be protected from overtly sexualised images but I disagree that the downfall of Western Civilization is in any way attributable to porn, and completely disagree that the answer is to demonise human sexuality and hide it away, censoring anything and everything that we don't like. I'm of the opinion that kids should be taught - by schools and especially by parents - about all facets of sexuality as soon as they're able to mentally process what they're being taught so that they can better understand why boys like girls and why some boys like other boys and some girls like other girls and why some boys don't want to be boys and why some girls don't want to be girls.
I think that the root of any societal problem caused by porn - and the types of porn that you mention - isn't simply that it exists, or even necessarily that young people might be able to access it, but rather that we don't teach kids about this stuff. We don't try to help them understand why any of it exists, we don't teach them about fetishes and why fetishes exist and why and how some fetishes can be dangerous, we don't teach adolescents that the sex depicted in porn is not realistic, that most women don't look like that, that most cocks aren't that big, that the absence of explicit consent in a lot of pornography is something that should never occur in real life sex, we don't teach them about addictions to pornography that can negatively impact their sex lives or that porn is not a substitute for sex and companionship with another human being. Censoring porn isn't going to help kids understand any of that. If anything, it's going to make it harder for kids to understand.
Everything, you said makes logical sense, and perhaps the answer is as simple as education. Although I don't know if explaining much of this stuff to tween is a good idea, much less how a parent would go about explaining fetishes.
But I think what's important to understand is that this is all one giant social experiment, that we have been rushing to at crazy fast speeds. 5 years ago, you were hard-pressed to find free live sex shows on the net (MFC banned performer from doing them, as did almost all other cam sites.) I'm not sure exactly when Tube site became popular but I'm going to say within the last ten years. I do know (since I did it) that at the turn of the century if you typed in "Gangbang" to the premier search engine of the time (AltaVista) you get hundreds of hits for porn websites. In virtually all cases while you see plenty of pictures of naked woman, cocks, spread shots, dildo in vagina were all pixelate or rarely limited to still images. If you wanted to see videos, you had to produce a credit card and typical pay a $1 or $2 for a preview, and $10-25 for a month access. It was possible to get free hardcore porn, but it was beyond the capabilities of most users, and while I'm sure that determined teenage boys still found porn, I think it was a lot harder for kids under 12 to find it. I know there are a number of folks on the forum, who would have been around 12 in 2000 so feel free to tell me I'm full of shit and that you were regularly watching gangbang or whatever videos at that age around the turn of the century.
The US is has gone down the path of making hardcore porn readily available to children. The US constitution as well as Supreme Court decision pretty much assure that we aren't going to down Britain's path. It appears that most Europe is doing the same thing. Countries like China, most of the Middle East and parts of Asia are making it hard for kids to access porn.
Which path is going to produce healthier children? Hell if I know, and I can tell you that anybody who claims that do know is full of shit. It is illegal to show kids porn pretty much everywhere and so there very little research, and what little there has been focuses on teenagers.
I think what the UK doing is a good idea, simply as control group. So that in 20 years when sociologists look at the impact of exposure to porn on young children we aren't trying to figure out who's kids are more fucked up the US or Saudi Arabia, but rather a country more like us the UK.
